Pokemon Mystery Dungeon: Explorers of Darkness

I need more info cuz i don't know what you're talking about.

I'm pretty sure you don't need an extra slot on this game. Keep training your ninjask and keep checking in at Luminous Spring. Your Ninjask should eventually be able to evolve. Mystery Dungeon doesn't work the same way as the other games so whatever source you got that from should be specifically for Dungeon.

Lol it evolves from nincada at the same time as ninjask. If you have an empty slot, the shed skin becomes a shedinja (according to serebii.net), so...

When nincada evolves, it "sheds" it's skin to become ninjask. The skin has a life of its own, becoming shedinja.

You are probably reading from the DP/RSE guides on Shedinja. In the original Pokemon RPGs, you had to evolve your Nincada when there was one empty space on your team, and a Poke Ball to spare in your bag. The Nincada would be replaced by a Ninjask, and the empty space would be taken up by a Shedinja out of nowhere. There are no 'slots' in PMD, and I do not believe that it is referring to space on your team.

I don't know really that happen to me before

What happened is that once you evolve nincada into ninjask, shedinja automatically is sent to the recruitment desk.I've done it before.

Use hold item or raise other stat.

Talk to to chimecho....

Horizo why talk to chimenco, is no solved. You can use iron and ect to raise stat and hold item.

when you elvolve nincada (or sommething) it turns in to a ninjask and its hollow, shed, skin becomes "SHED"ninja

You're probably looking at an answer to the mainstream Pokemon games (e.g. Diamond, Pearl and Platinum). When you evolve Nincada in Pokemon Mystery Dungeon, the Nincada will become a Ninjask and a Shedinja should also appear in your Chimecho Assembly list. This is normal- even on the main games you get both a Ninjask and a Shedinja from a single Nincada.