You can build an application straight from your source: a connected GitHub repository, or any public Git URL.
Connect GitHub
A GitHub repository source needs a GitHub connection on your billing account, made once through GitHub's usual authorize screen. After that, the Repository field on the create form is a list of the repositories your connection can reach.
What the connection can see
The connection is granted enough access to read your repositories and set up a push webhook. Connect an account or organization you are comfortable giving that access, and remove the connection in GitHub if you stop using it.
Pick a repository and branch
Choose the Repository, then set the Branch to build from. Leave the branch at the repository default if you are not sure. The platform clones the branch with your connection's access each time it builds.
Deploy on push
Turn on Deploy on push to rebuild and deploy automatically when you push to that branch. Only pushes to the exact branch you chose trigger a build, and the push has to come through a verified webhook, so a misconfigured or unsigned delivery is ignored rather than trusted.
If you push again while a build is still running, the newest commit is held and built once the current build finishes, so a burst of pushes does not queue a build for each one.
Public Git URL
To build from a repository you are not connecting through GitHub, choose Public
Git URL and paste a Repository URL. It must start with https://; SSH and
other schemes are not accepted, and the clone is anonymous, so the repository has
to be public. A Git URL source is never push-triggered: you deploy it yourself.
Choosing what builds it
Both sources build with a builder. Leave it on Detect
automatically unless you have a reason to force a specific one, such as a
repository with a Dockerfile you always want used.