I have a 07 subaru sti and when I turn it makes a popping sound can someone tell me what it can be?

The popping noise you're hearing while turning is most likely your CV axles. Extra load is placed on the joints when turning. If worn they will "skip" and make that "popping" sound you're hearing. Check the axle boots for rips and tears. You may see grease being flung all over from the boots being torn. Also this allows water and debris to enter the joints causing premature wear. I would recommend replacing both. If one is worn, the other side isn't too far behind.

Check and make sure your DCCD isn't set to full lock or extremely aggressive on manual mode.

On that dccd what should it be roughly

To troubleshoot it, turn it all the way open and leave it on auto. If the popping goes away, it was the DCCD. If it's still there, it's likely a CV like Mark suggested.