Teams is a groupware, where you make collaborative groups, work on projects, chat, share files or have meetings.
1) You can log into Teams in a browser by going to office.hi.is and choose the teams app at the top of the page: 
2) You are now on the Teams site on the web. You can use Teams in the browser or you can setup the Teams app on your device. In the upper right corner you should see a picture of you (or initials if you haven't added a picture yet). Click the picture and choose „Download the desktop app“ or „Download the mobile app“ depending on the device:
3) On the left side menu you find a few options.
- Activity: Lists all your activity on Teams
- Chat: Private chat with one or more people
- Teams: Your groups, group chat and group files
- Assignment: Projects with a class
- Meetings: Calendar and meetings
- Calls: Phone system, only visible in departments that have implemented Teams calls
- Stream: Video streaming
- Files: Files from groups and OneDrive