Introduced is the tricky word here. It was known back in the roman days as a medicinal herb, but only ("introduced and") used as food in the 8-10th century (scholars do not universally agree on a more specific time).

Here is an excerpt about cultivation:

IV. Rice cultivation in Europe

IV.1 Spain The Arabs had established riziculture very early on in Spain and were exporting it from Sicily by the tenth century. The claim that the Byzantines were growing rice before the arrival of the Arabs is based upon the statement of historian Joan Corominas who notes that rice was grown in the southeast of the Iberian peninsula in the seventh century when the area was under Byzantine rule. Unfortunately, he does not provide any sources for the claim. Traders could find rice in Levantine ports. In fourteenth century, Majorcan rice was sold at fairs in Champagne.

IV.2 Italy In Venice, a deliberation of the Council of Ten in July 7, 1533, exempts rice from an excise tax because it takes the place of vegetables. The Provincial writer Quiqueran de Beaujeu wrote in 1551 of riceculture in Provence. One can't help but notice that rice was being eaten in Europe before the development of riziculture on the Lombardian plains. The fourteenth-century cookery manuscript known as the Libro per cuoco by an anonymous Venetian gives a recipe, rixo in bona manera - that is, a kind of porridge of rice cooked in almond milk with sugar. In Italy, a person who laughed easily was said to have eaten rice soup, a play on words : che aveva mangiato la minestra di riso (he had eaten laughter/rice soup). Rice is synonymous with Italian cookery in the form of risotto, which is produced from the stubby, short-grain varieties. Risotto shares many similarities with the Spanish dish of paella, which claims Valencia as its standard bearer. This common bond is indicative of both the trading links between the two sets of seafaring peoples and the conquests and counter-conquests of the various kingdoms that fought for power in the region during the course of the 15th and 16th century. While other areas of the Italy have developed rice growing, such as Emilia Romagna and Tuscany, the Po valley remains the spiritual and most fertile area of cultivation. And not surprisingly it is the area where rice consumption is at its highest. The early rice dishes, which were baked or fried, did not have an influence on other neighboring regions until the Spanish Aragonesi took them to Puglia and Campania in the thirteenth and fourteenth centuries. Botanical gardens experimented and soon the monasteries discovered the benefits of this economical crop. By the fifteenth century we find the Benedictine monks at Montecassino carefully selecting the best of the available seeds and starting extensive cultivation. In the north, soon to become the center of Italian rice cultivation, we can find probably the first mention of rice in the early fourteenth century in the household accounts of Torino's Duke of Savoia, and it is recorded in 1475 that Milan's ruling Sforza family sent twelve sacks of seeds to the Duke of Ferrara. Cultivating rice was very labor intensive in the spring when the land had to be dug over and fertilized after the hard northern winter. The seeds had to be soaked in water before planting so that they started to germinate before being sown and the rice fields had to be flooded with water from the canals so that the seedlings would be protected from the sharp drop in temperature during the night. However, the real back-breaking work was the weeding. In May the rice fields had to be weeded to prevent the young rice from being choked by other vegetation. Hundreds of women known as le mondine, or weeders, arrived from all parts of Italy to perform the delicate task of rooting out the weeds while leaving the young rice in place. It was a hard life for le mondine, living together in dormitories housing hundreds of women far from their homes. They had to work bent double, up to their knees in water under a blazing sun. They were bitten by mosquitoes and the water teemed with wildlife. They worked in rows, moving backwards, controlled by an overseer who sat high on a chair like a tennis umpire. When the women approached the end of a field the overseer called out for the central girls to move out in order to leave a space for the frogs (which had been driven back as they progressed down the field) to escape. It is said that the water seemed to boil as all the wildlife made a mass exit. As the women weeded they sang. One of the songs, Ciao Bella, was adopted by the Italian Communist Party to express the social injustice of the system. Le mondine and their songs have disappeared and modern machinery makes rice cultivation much easier. from: https://www.zum.de/whkmla/sp/0910/chef/chef1.html

There are a ton of resources if you just google this question, or if you are in search of a more specific answer, you'll have to clarify your question.