Credit to u/asdf23451 and Dantheman827 for this.
Also my Reddit account is u/_-iosuserloaded (for more help).
Since Impactor, ReProvision, and almost all 3rd party "Sign it yourself" signers are broken, I've decided to update the guide for iOS App Signer, since some of Xcode's Layout, as well as iOS App Signer, have changed.
If your jailbreak isn't on jailbreaks.fun, or it is a different app, or you just want to sign it yourself (because you hate revokes, or like learning things), then this is the guide for you.
An Apple Device, and a way to connect it
Xcode. Download it from the Mac App Store or From Apple's Dev website. (This Guide is updated for the new versions)
MacOS (Virtual Machines and Hackintosh work as well)
For Windows users who want Unc0ver, it is easy, however, I cannot link on name the tool. Beware as it is a bit sketchy.
An Apple ID
The iPA of the application