What would be a good transparency editor.

I dont know what to use. I have to pay for photoshop and GIMP doesnt work

GIMP works. Explain what you're trying to do, and I can help you.

i wanna modify it so the transparency is clear on the empty spaces. I want to do it for my custom tiles. Id be appreciated.

Paint.net is great. I know the gimp can do it too, but its a lot simpler to do it in paint.net.
You just take the magic wand tool, turn down the sensitivity to 0 (there is a slider at the top of the screen), click on anything you want to make transparent, and press delete. (or dlt if you have a keyboard that doesn't have all the words spelled out properly.)

Paint.net is great. I know the gimp can do it too, but its a lot simpler to do it in paint.net.
You just take the magic wand tool, turn down the sensitivity to 0 (there is a slider at the top of the screen), click on anything you want to make transparent, and press delete. (or dlt if you have a keyboard that doesn't have all the words spelled out properly.)

What you describe can be done exactly the same way with the GIMP (maybe the Magic Wand Tool is called differently). If that's what GangstasFORLife3000 needs, he can use either program. But yeah, Paint.NET is better for pixel art than the GIMP, which is more suited to photo editing.

Personally I think GIMP is more suited to everything than Paint.NET, it's just more resource-demanding and a little more difficult to learn.  Of course, opinion.

Also, a better way to make a single color transparent is to use the Select By Color-equivalent tool instead of the Magic Wand-equivalent tool.  In either case, make sure sensitivity/theshold is minimum (usually 0), and that options like fuzzy select and antialiasing are off.

What you describe can be done exactly the same way with the GIMP (maybe the Magic Wand Tool is called differently).

Weird. I usually have to do a bunch of things whit layers and settings for it to work in the gimp.

I tryed to do the magic wand stuff with the paint.net, When its on knytt stories, Its black instead of clear. Now what

Paint.net can be a little finiky. If it appears black in KS, open a custom tileset by some one else that has a pink background (you wont be able to see it in KS). Eye-drop that colour, and replace the transparency with it. If you cant find a tileset with that colour, i think its values are blue-225, red 225, but i'm not sure

About transparency, you might want to read this topic, or search for other similar topics to find out some useful techniques in Paint.NET and the GIMP. Regarding your specific issue, PNG can be both 24 and 32 bit: in the first case, transparency in KS is made with magenta (the colour a clockwork lemon was suggesting), but you can't do translucent tiles, so keep that in mind for your work.

I tryed to do the magic wand stuff with the paint.net, When its on knytt stories, Its black instead of clear. Now what

Save it as 32-bit instead of auto detect.

Thanks, Saving it to 32-bit works. I can edit tileset transparency without photoshop, Thank you all.