hello yesterday I registered on freely wordpress blog but I did not found plug in tab and If I buy a domain from wordpress the plugin will activated!!
deactivating all plugins to see if this resolves the problem? If this works, re-activate the plugins one by one until you find the problematic plugin(s). - switching to the default theme to rule out any theme-related problems? - resetting the plugins folder by FTP or phpMyAdmin? Sometimes, an apparently inactive plugin can still cause problems.
freely wordpress blog?? do you meen that your wordpress blog is restricted untill you purchase a domain?
Not sure about this as I've never used free WP hosted blogs. I really suggest you invest in your own domains though - not only will you get SEO benefits from the EMD - but you can customize it however you like, and can also sell it later on. I think GoDaddy are having a .com promotion for only $2.
plugins on free hosting is not allowed i think, or else i would have installed myFtp plugin for wordpress to upload all my files on their server