I cannot find the installed program

Hi there,

for example i tried to download pidgin. I did this with the following command:

sudo apt install pidgin

This also works so far, only after the installation I don’t know where to find it and where to run it.

Just open a terminal and type

That should do it.
If you want to keep pidgin beyond reboots, install pidgin in the corresponding template.

These guides should help you: How to install software | Qubes OS and App menu shortcut troubleshooting | Qubes OS.