Work on your feature branch and commit on your feature branch. Create Pull requests against dev branch. If dev branch has a solid state a pull request against master will be done.
After checking out your branch, please merge dev into your feature branch to always be up to date.
Create an Issue in the Issues Tab. Go to Projects, click on "add cart" top right and add your issue to the desired column on the board. If you're done working on the issue, or if you wish a check of your code, move the issue to In Review or Done section.
If you need something to be done by another colaborator, create an issue and add an assignee on the top right of the page.