On the left navigation bar, click the item near the top labellednext to the parachute icon. This will bring you to the deployments page. You'll notice there are three columns: Commits, Staging, and Production.
Commits is a list of all the commits that Truffle Teams is processing, or has processed, as a build. Each will have a status icon to show if the build is in progress, failed, or successful. Commits with a successful icon (a green box with a checkmark, as pictured) will be able to be deployed; thebutton in the top right of the commit indicates this.
Staging contains a list of all testnet (i.e. Ropsten, Görli, Rinkeby, and Kovan) and sandbox deployments. Production contains a list of Mainnet deployments.