Remo, welcome to Project Online (I assume that’s your trial). If so you have two options. To be honest, you are looking at either a lot of reading and research with sporadic results or solicit support from an expert…or a combination of both. You have a long road to get a true picture of what Project Online can provide.
If you are referring to Microsoft Project the same is true but you can use and get value from Project to the extent that you know it, so it’s a bit easier to buy a book and learn on your own.