[RMVX ACE] CUSTOM TILE IMPORTING/TILESET MAKING ISSUES

Hi, I'm kinda new to RPG Maker, but I've been watching plenty of tutorials and I feel as if I got a pretty good grasp. The problem though, is that I have trouble importing my own custom tiles that were put together in photoshop and making them into a proper set. I've tried using a direct template that had a full tile set that was already in the program by default, and it imported just fine, but when I tried to put it into a tileset, most of my tiles were cut off and only a few of them showed up. (Most of the tiles you see here are just cut and edited from the old pokemon games)
These are the tiles that are getting cut off.

Yet this is the full sized image.


I kept trying to google for answers, even search on youtube for solutions, but most tutorials only talk about creating new tilesets from tiles already implemented into RPG Maker. I'm not sure if it's a naming issue, if the entire picture HAS to be filled with tiles for each square, or if i'm not organizing them well enough...
If anyone can explain what I'm doing wrong that would be a m a z i n g!
Thanks!