Installing Briar via F-Droid
1) Install the F-Droid app.
2) Open this link on your mobile device. (If you're using Firefox, long-click the link and choose Open with F-Droid App.)
Or scan this QR code on your phone:
3) Choose F-Droid, then click Just Once.
4) When the Add new repository screen appears, click Add.
5) F-Droid will update the list of available apps. When it finishes, search for Briar in the F-Droid app.