Welcome to TFP!!!
Since it is a DE filter here is what I do:
-Put the correct amount of DE in a bucket and then fill the bucket up with water ... I mix this up with my arm to make it into a slurry.
-Open the air vent on the top of the filter
-Turn on the pump until water comes out the top of the filter
-Close the air vent and turn off the pump
-Take the bucket to the skimmer, take the lid off the skimmer, stir up the slurry again
-Make sure all suction is from the skimmer if you have suction valves
-Turn on the pump and start to slowly pour the DE into the skimmer
Once you have added all the DE, note the pressure on the filter and that is your "clean" pressure.
When the pressure rises 20-25% over this pressure it is time to backwash and add more DE
Here is more info about DE filters
use-and-care-for-de-filters-t4086.html
Now, since your pool is green. It sounds like you need to start the
Shocking Your Pool PROCESS with requires one of the
Recommended Test Kits
While you are getting started, Please add your pool details and location as described
HERE to your signature as it will help us help you.