all post the directions so someone who searches this topic will find it to have answers.
step one make a brush
step tworight click on the brush and select Func-->door
step 3 open the entities window by pressing N
step 4enter this info
key speed
value 250
step 5make sure the direction is up
step 6 press esc
step 7 compile and you should have a working door
for a more compete tutorial go
here