what are the steps to such thing, i want to write an episode to beavis and butthead and send it to MTV ,i don't live in the USA,i don't know if that a problem , please provide me with all the details that can help.
While I don't work in the TV industry, as I understand it, most shows have their own stable of writers and generally don't accept unsolicited manuscripts. (Some of the Star Trek shows did, but I gathered that was unusual.)
At the very least, if you do want to write for a show which does accept outside manuscripts (and I don't know of any), you would need to get an agent to submit it for you. Even a show which does take manuscripts from out-of-house writers is not going to take one without representation.
ETA References. The upshot is "it's extremely probable that you need an agent, but there's an outside chance you can get by without one."
Writer's Guild of America: Companies with episodic television shows and once-per-week serials must hire freelance writers each season for each series, depending on their network order, but it explicitly says you must have spec scripts for an agent to submit. A lot of good instruction at this link.
About.com: "You must secure an agent to be considered a professional writer."
Two references for companies which will apparently take unsolicited scripts without an agent, in the UK.