In order to find fuel stations and other POIs easily, we highly recommend to use offline maps (only available in the Pro version). With offline maps loaded you can go to the
Map Layers, and select to show the POIs you are interested in. The POIs you checked should show up on the map in a 30x30km (about 20 miles) window. Once you zoom out further they are removed to avoid cluttering the map.
If you have a pre-planned route, it should be easy to spot a fuel station along your route. If you want to plan your route along this fuel station, zoom into the map a bit and just long press on the map where the fuel station is located and select
Add via point.