Because the Store is dead, you cannot simply tap and install. You need a specific toolkit:

Community-driven repositories that offer modified app stores for unlocked devices.

Because Windows Phone is a deprecated operating system, finding a "full archive" of .XAP files (the installation format for Windows Phone apps) is not as simple as visiting an official store.

If you want links to specific verified archives or help unlocking your phone for XAP deployment, let me know.

: For basic system apps and developer utilities, the Microsoft Download Center still hosts some Windows Phone 8/8.1 offline installers (.xap) for the time being.