(Linux newbie) Trying to play doom via doomrunner and it keeps giving me this error (See picture)

[bugerkin]

Trying to play doom via doomrunner and gzdoom and it keeps giving me this message when ever I hit launch.

[summer1090]

deb is package file with engine, you need to install the package first and only then select the gzdoom

[Youda008]

As summer1090 said. The .deb file is an installation package, something like the .msi on Windows.
It's not a program you can immediatelly run. You have to install it first
https://askubuntu.com/questions/40779/how-do-i-install-a-deb-file-via-the-command-line
then find the installed executable (usually in /usr/bin, /usr/local/bin, ..., you can use which command to find where it is) and add that one into Doom Runner.

[bugerkin]

So I did what you told me to do in the terminal but for some reason I can't change the executable. (I'm clicking the folder icon and trying to select the executable file but It just doesn't work)

Also I thought I could fix this problem via reinstalling through linux mint's software manger but now I can't change the theme, Add both the Doom 1 & 2 Iwads and add any map packs.

[Youda008]

You need to click Menu -> Initial Setup and edit it there.

[bugerkin]

Sorry for the late response but everything works now after helping me.

Thanks!