To add an account on an IM service, make sure you have an account with that particular service. Then click the Accounts tab:
- Tap the Accounts tab.
- Tap the [+] button at the top-right.
- Choose the appropriate service for the account you're adding..
- Input your username on that service. Note that some services use full email addresses.
- Input your password to that account.
- Tap the Done button.