These steps assume you have already connected your repl.it account to your GitHub account.
In repl.it click the button to create a new project.
From the "New Project" pane, click the "Import From GitHub" tab.
Enter the GitHub repo URL or type in the username and repo name. Then click "Import from GitHub".
After the import, in the left pane you should see the project files from the GitHub project.
Click the "version control" icon.
You should see the GitHub project name, and it should show you up to date with the main branch.