I have a website and want to pushing about 15 keywords, any body
can experinces about pushing a website with many keywords? how i
must do? Thank you

You mean you want to top for all 15 keywords for your site. If YES then you will have to work hard on SEO and would have to do lot of research on what others are doing ;)
If your targeted keywords are much popular and have much competition then you will have to work very hard to get better ranking for them.

optimize your page using your 15 keywords. You can place the keywords on your metas( title, keywords and description)

It seems a very tough target by now u must have seen some results why dont you share with us .how much u have achieved by now

If you want to optimise your website for 15 keywords allocate key words to pages accordingly and design metas for each page using those keywords.