Here’s a map to the double jump.
Map to Double Jump
You can use this to show you where to find the double jump. Follow this and you’ll get the achievement “Breaking the sequence” for getting the DJ before fighting any bosses. Go to the green dot on map.
You will need to do some wall-jumping to get there but it shouldn’t be very hard. Just a little practice and you’ll get it in no time!
Hope this helps!