First set it up in Docker with the following commands. Since you said you have been trying to get it to work for a while I included the docker stop and docker rm commands just in case an installation is running.
Make sure to replace the USERNAME and PASSWORD with your frndly username (e-mail) and frndly password. A lot (I repeat A LOT) of people seem to not do this. You need to add your Frndly e-mail address after USERNAME= and your Frndly password after PASSWORD=.
Then follow the double source method as described (with pictures) in post 546 of the Frndly thread.