These directions are for iOS/Apple devices but the general idea is the same for Android.
Step 1: Launch the Teams app from your home screen of you can search for it by doing the middle of the screen swipe down and typing in “teams”
Step 2: Click “Sign in”
Step 3: Enter your work email address and click “Sign in”
Step 4: Click “Allow” to the popup
Step 5: Click “Ok”
Step 6: Click Next
Step 7: Click “Got it”
Step 8: You are now signed in