im new here and i want to know if you half to notify the person or something when u use their tileset to make a level to post on J2O

Nope, ppl dont, although I have had myself noticed on a couple of occasions (thats when they actually use your set, Agama rules all).

Strictly speaking , i don't think it's obligatory. but actually yes, you're expected to mention who made any custom tilesets you used in your level. which makes sense, doesn't it? the tileset maker made an important contribution to the level

And Blade asks that anyone who uses his tilesets tell him, so that he can review the level in question.

Oh, then I need to tell him about my new level

I never do. Hah.