Engine Swap new computer

i have a 84 Nissan king cab that i recently swapped the motor out with a 87 Nissan and i can get it to turn over but i cant keep it running. it came with a new computer but i cant figure out how to put it in or where it even goes i was told under the drive.

It turns over but im not sure how to hook up the cpu unit so i cant keep it going i was told it was vac lines that's why it wont stay running but i dont know where the cpu goes or how to hook it up?

This site is a life saver :-)