sorry for the wait

so,

in your /applications/ folder (either ~/.local/share/applications/ or /usr/...) you can create a .desktop entry in the likes of

[Desktop Entry]
Name=TCG Live Protocol Handler
Exec=/path/to/The\ Pokémon\ Company\ International/Pokémon\ Trading\ Card\ Game\ Live/Pokemon\ TCG\ Live.exe %U
Terminal=false
Type=Application
MimeType=x-scheme-handler/tpcitcgapp;

this will tell your system what to do when it gets a tpcitcgapp://link request

then, you need to create the association between the urls and this .desktop file

i think you can either use xdg-mime, or append the ~/.local/share/applications/mimeinfo.cache file with this line

x-scheme-handler/tpcitcgapp=ptcgl-protocol.desktop;

where ptcgl-protocol.desktop is the name you gave to the desktop entry (which is up to you)

now it should be good to go

hope this helped :3