How do I pin my project at the top?

This is a paid service. Go to the «Projects» tab in your personal account and select the desired project. Click on the «Edit» button, select the «Pinning» option and save the project, the payment page will open. After payment, your project will be fixed for 7 days. 

The options will be displayed only for published projects. The same can be done for a new project during its creation.