The general idea for setting up a build is similar across all platforms. Firstly you need to give Mobile Center access to your source control, then select a repository and a branch to build, and then setup the build configuration depending on the platform your app is being developed on.
The specific steps can be found on the platform-specific pages:
While in limited preview, some of the features might not be available to all users. If you have interest in a specific feature, but you cannot find it in the UI, contact us to get access to the latest bits.