MultiTerm is a program for managing termbases. You can create and manage a termbase with it. A termbase is not installed, this is more or less the same as an electronic dictionary and may be used after creation to deliver terminology in Trados Studio.

So in a nutshell:

• Install Trados Studio. Best way is to right-click the installation file and select "Run as admin"
• Install MultiTerm, same as before.
• Create a termbase, for example using an Excel sheet with some terminology using Glossary Converter from the App Stode (currently you need to use the private one, see above)
• Use this termbase in Studio
• If you wish to add languages or fields, modify the termbase using MultiTerm

The order of installation may not matter, but my experience since over 10 years shows, that installing as admin in that very order is the best way to avoid trouble,