How do you delete ThirdPersonExampleMap without UE4 freaking out?

I’m currently giving myself a shot at game development with UE4 for a game I’ve had in my head for quite some time. I wanted to properly test out my main menu so far in an executable file rather than the editor, and when the content finished packaging, it started me out by default on the ThirdPersonExampleMap, which I couldn’t seem to change. I couldn’t even switch the level.
So instead, I found the level titled “ThirdPersonExampleMap” and deleted it and it’s build data to see if it would help, but instead, it made it impossible to run the executable.
Unfortunately, due to some browser viruses I have, I can’t upload the image, but the error message reads:

“Map specified on the commandline /Game/ThirdpersonBP/Maps/ThirdPersonExampleMap could not be found. Exiting.”

Is there any proper way to remove the level without this happening, and is there any way to change the default level that the program starts up on?
Sorry if I’m being vague, I’ll answer any other questions people have.