This official site tells you how to apply for a work (or other) visa:

mofa.gov.bh/Default.aspx?tab...

thank u sir.i saw a form there to fill out about it.but is there an assurance that it must be granted

There is *never* any assurance that any visa application will be granted, regardless of the country. You just have to fill in the forms, make sure you have all the required documentation, take or send the paperwork to the appropriate authority and hope for the best!

is it not better to go through an agent.cause i heard u must have a sponsor

I can't advise further, I'm afraid, because it's not something I've done myself.

Yes. To get a work visa, you will generally need a company to sponsor you.

how do i get a sposor or company?

You need to apply for a job then be offered a job. You need to prove that you can do a job that a local cannot.

yes i know but i dont where and how to apply for any job at all.i mean the site to do that,thank u.

You need to apply for a job in Bahrain, if pass the interview then the company will arrange your visa for you.

You can not simple able get a work visa with out a job.

ok if i enter there with tourist visa,can i apply for a job?

You can apply for one but you can't actually take the job if it's offered. That's the same pretty much everywhere: if you enter a country with a tourist visa you cannot legally work.