If you install uiflow firmware you have also installed micropython. You can connect to a repl shell, load libraries, and modify main.py. You can use any micropython ide and you aren't required to use uiflow. It is a good option though. I like using upycraft. Even if I am running uiflow I'll still keep a connection to the board open with upycraft to get immediate feedback. With upycraft you have direct access to the filesystem and you can drag and drop files to and from the board. You can also run
where module is one of the listed modules. To learn more of all the built in functions available.