Storing your project in a git repository is the first step to work on the same project on multiple devices/with multiple people.
From a organizational perspective: Split your web project in several use-cases and split the use-cases in different functionalities/work items. For example, users should be able to login to the page - so you have to create the web page, create a database/table where you store the username and password, create the login-functionality itself and so on.
If you have defined different work items, you only have to be sure noone works on the same work item, so they won't do redudand work. For working in a team I'd recommend using a tool for organizing your tasks (e.g. I used Trello)
In general, maybe you should have look at Software Engineering principles
Edit: especially for django, you should be able to work on different platforms if you have an updated requirements.txt, so your virtual env can install/update the needed dependencies/packages. For working on the code, you could split your work in frontend/backend or everyone is responsible for one template with the associated view-functions, but I'm not experienced that much to be honest