Hi welcome the community,
You can’t install another printer in Printershare app from your app.
With activity starter you can open Printershare from your app and send a file so that it prints it (I believe that, don’t test).
I don’t know much about Printershare app.
Not all option available in Printersare are free. Perhaps need to use the version he pays ??
Check if the printer that you want to use is supportted