how to work with a second display and lid closed

i have a question. i am trying to run a single display while my mac air is closed. its not working though it just goes to sleep as soon as i close my mac lid. i have a bluetooth keyboard hooked upto it and have bluetooth set to be allowed to wake up device but its not working. so i hooked up a usb mouse and that doesnt work either to wake it up. ive been messing with this for 45 minutes and im starting to get ****** off. i never had this issue before. can anyone help.

ok im an idiot. i just remembered this has happened to me before. you cant run off of an external display with the lid closed unless the ac power is plugged in. it wont work on battery. working now.