Just a heads up. DO NOT place the sliding images in a nextgen gallery. You need to add it directly to your media library or sliding door won't find it. Took me two hours of messing around with code to realize that it was just that simple.
Make sure you clear your blog's server cache! That is why you're not seeing changes you made. You'll need to go to the cache plugin's support forum for further help if you have no clue what I'm talking about.
And just in case, a picture is worth a thousand words. How to add the sliding door menu:

- Instructions on adding sliding door menu
- Sliding-Door-Instructions.png (89.12 KiB) Viewed 10044 times