keeplaptop active when lid closed

[scraginagpup]

I am running xenialpup 7.5 on an old laptop. I want to use an external monitor, but want to be able to keep the laptop active when the lid is closed. I thought I remembered there being a config file with a line "suspend=1", and the "1" had to be changed to "0" but I can't remember the name of the file...or maybe there is a better way of doing it?