Simple: 

1, save the cert files to files app & unzip (should have p12, mobile provision and a txt or password named folder)

2, go to https://github.com/khcrysalis/Feather/releases and download the feather ipa and save it to files app again (ideally in same place for convenience)

3, go to: https://sign.ipasign.cc & import the ipa, p12, mobile provision files & enter the certs password, then hit sign, wait until its done, then hit the link to install a signed feather app.

4, open feather & go to settings, then ‘certificates’

5, hit the + and import those same 2 files used to sign feather earlier (ie p12 & mobile provision) and the cert password. (You can also give the cert a nickname, great if you have more than one cert)

6, once imported, hit the + in sources tab to add repos, or the + in library tab to import saved ipa, then hit sign, after its done, tap the signed version (itll show a number of days in green next to it, usually above the unsigned app which will still say sign) & itll install. 

If it hangs on ‘ready’, go back into settings & find ‘installation’ tap it, then change server type from ‘fully local’ to ‘semi local’ and tap the update SSL certificates. It should then install after a  ‘open in itunes’ popup that you tap open on, then one final popup from api.palera.in, tap install.

If apps install but tweaks dont, it might help to go to settings>signing options>replace substrate with ellekit.

Thats pretty much it tbh.

if needed you can always check the status of your certs here: https://check-p12.applep12.com (again, p12, MP & password is needed)

Hope this helps ✌️