Hi TrobbizSH,
First of all thanks for giving our game a go!
To answer your question, the items automatically go into your inventory which can be found at the crafting station (if this is not happening then it must be bugged really sorry if it is), to craft things you need to go the crafting station to craft more fuel then add it to the engine.
We didn't get all that we would have liked to done in time so I completely understand you being confused, we really would have like to add a tutorial and more things to do overall, we can only try to do better next time though :D.
Thanks again and if you have anymore questions just let us know!