In addition to Daniel's suggestion, I would recommend the built-in help of Studio - there are several pdf documentations available on the Get Started tab in the Welcome view.
And also there are training materials in your SDL Account under Support&Education > Education.
As for MultiTerm, it is an advanced terminology management software, and it is usually not needed for general translation jobs. In case your work entails terminology-related tasks, you might need it though. But it all depends on the jobs you'll take on.
Greta Magyar - Customer Success Representative - SDL