how do i use my laptop as a monitor for my desktop computer?

Answer:

You can use desktop monitor as a monitor for your laptop, but you CAN'T use your laptop as a monitor for your desktop.
Get a docking station.
a tv card resolve your query
get unadulterated and get a monitor they are straightforward to buy and find at Goodwill's and such...
it should be another way around not laptop as your desk topmonitor
u cant