Follow these steps to add your custom modules to Odoo.sh:

1. Get your git repository in your local machine, add the my_library module in it, and then execute the following command to push the module in the GitHub repository:

git add .
git commit -am"Added my_library module"
git push origin master

2. Open your project in Odoo.sh. Here, you will find a new build for this commit. It will start running test cases and you will see the following screen:

3. After a new commit is pulled in your Odoo.sh project, you will see the installation progress on the right side. Wait for the installation to be complete then access your instance by clicking on the green CONNECT button. It will open the Odoo instance with the my_library module:

Explore and test the my_library module. Note that this is not a production build, so you can test it however you like.