i upload a skin and tht is not showing where we change skin in page setting's appearance?

I assume that you installed the skin using the WIzard on the Extensions page.

Skins can be installed as site skins or host skins and there is a radio button on the page settings to choose which type to use for your page. Did you check settings in looking for your skin?

i install them from admin extension and i used for both.i m using community addition.

If you have access to the website directory, look and see if the skin is actually there.

Look in Portals/_default/Skins for the globally installed skins.  Look in Portals/N/Skins (Where N is the number of the portal) if you installed the skin as a portal skin.  There should be a folder with the name of the skin in the Skins directory and a similar on in the Containers directory.  The html, ascx, and skin.css files should be in the root of that directory.  If not, there was a problem with the way that they were installed.

nothin is working with this.will u explain me with step by step procedure.or i m using community addition so this facility is not available with it???

Is this a skin that you have developed?