The process of coaling a ship was pretty banal, and happened mostly like you think it would. [Coal](https://upload.wikimedia.org/wikipedia/commons/0/0e/HMS_Majestic_(1895)_at_coaling_station,_retouched.jpg) was dumped into the ships bunkers useing lifts and crains to manuver coal shoots into place. From there, the ships bunkers would be resupplied with fuel, as well as fresh water which was a critical and often overlooked part of the coaling process. The coal was usually imported under contract aboard colliers, which were either private ships or commissioned naval vessels (depending on the time and country in question) whose job it was to basically haul coal from point A to point B. Again, where the coal came from was very dependant on when and who you are talking about. Because coal is not perishable, coal could be shipped from coal rich regions in Europe and the United States to coaling stations around the globe. This meant that Europeans bought their coal on a global market, and would import coal from wherever convenient.

In addition to the actual coaling facilities, each station was also a small military base. Places like Guantanamo Bay were small self contained enclaves in larger nations, and served to defend the coaling station. But in places across Africa and Asia, coaling stations could also serve as bases from which European nations projected their influence. Regardless, Coaling stations were important naval bases, and a hostile navy could potentially operate out of them at will. This made the bases convenient strategic locations for powers who were interested in gaining influence in a region and penetrating deeper into the countryside. So some stations could be the locus for major military and colonial activities, while others in more out of the way locations would be much smaller and less defended. Again, it really depends on when, who, and where youre talking about. Guantanamo Bay served a different purpose than Gambia, which itself was different than Singapore.