If you are coming from the south, you need to go over the traffic lights at the intersection with Popes Lane/Gunnersbury Lane and then the next left is Baronsmede/Gunnersbury Drive. Go past that turnoff but then you need to be on the lookout for a turning to the left into the ground - it will only be about 100 - 200 yards. The turning into the ground is pretty much opposite Kingsbridge Avenue on the other side of Gunnersbury Avenue. You should see the sign to the ground on your left.

If you are coming from the north, the ground can be accessed by turning right off Gunnersbury Avenue/North Circular Road. If you head south from Uxbridge Road, you will go past Crosslands Avenue and Evelyn Grove on your left. About 200 yards after you pass Evelyn Grove on your left, you need to look out for the entrance to the ground. Shortly before the turnoff, the road passes over the Piccadilly Line and therefore when you see the break in the houses on both sides of the road, you will then be very close to where you need to turn to the right. If you go past Kingsbridge Avenue on your left, you have gone too far.

The following link may help:
https://www.google.co.uk/maps/place/Popefield+Playing+Fields/@51.5027074,-0.289032,16z/data=!4m5!3m4!1s0x48760de52e7ef153:0x20280db6bdf4d95e!8m2!3d51.5038061!4d-0.2914488