You can find all the available apps on the Market page. The table shows each app affiliate's terms, such as 'Commission rate' and 'Minimum withdrawal.
Once your connection with an app is approved, it will appear on the Connected apps page.
The connection request
When you find an app you want to promote, You can connect with it using the 'Join affiliate program' button. A popup will show up, where you'll be able to review the affiliate terms. Once you apply, the request will be sent to the app owner.