Here's a step-by-step guide on how to use Skype for Business:

1. Plan for Skype for Business.
2. Sign in to Office 365.
3. Set up your domain and users.
4. Set up IM and presence in your organization.
5. Download and install Skype for Business.
6. Test to make sure everything is working.

You can find more detailed information on each of these steps at [Microsoft's official website](https://learn.microsoft.com/en-us/skypeforbusiness/set-up-skype-for-business-online/set-up-skype-for-business-online).