While much more can always be said, I summarized the current academic consensus on the origin of Kievan/ Kyivan Rus' and their relationship with the "Vikings" (Varangians) before in: How come there isn't a greater Nordic/Viking influence on Russia and its language even though the Kievan Rus' was at first ruled by Varangians?

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In short, The ancient name of Rus' is generally said to have derived from a group of Scandinavian people also active in Russian waterways in the 9th century, and some of their cultural elements as well as themselves were merged into the new ruling elites in Russia, such as Kievan/ Kyivan Rus', by the end of the first millennium.

On the other hand, some western Slavs on the southern coasts of the Baltic built more complex relationship with the Scandinavians (especially Danes and Swedes), as I also explained in:

• What were the relationship of Rus' principalities after the 10th century with Latin Europe?: alludes to the political-religious breach between the East (Slavs in Russia) and Western Europe by about 1200 CE.
• Slavic vikings?: answered by /u/Platypuskeeper and me
• Where did the Piast dynasty originate from?