If you are new to Vem, the best place to start is its tutorial:

If you want to learn Vem more in depth, you can check Vem user's guide, which explains all Vem commands:

For quick reference, you can access the cheat sheets for each keyboard layout. There are two versions of each cheat sheet, a basic one with only the most important commands —very useful if you're starting with Vem—, and a full one with the complete list: