How to install python 3.11 on glitch ? current version is 2.7. Or how can I create my python environement

I want to host an flask api on glitch and its required the python 3.11. How Can I install the python 3.11? Or how I can create my own python environment. to separately install my specific libraries?

flask docs say it needs 3.8+. is it something else that needs specifically 3.11?