I need to verify my site with google webmaster tools,but i cant find a place to paste their code on

Are you talking about Hubpages or your own personal website. In case of HP, there is no need to verify. In case of your website, you have 2 options:

1. Open your index page in frontpage express > Right Click > Custom > Add > Now add "Verify" Under name and the value under "value"

OR 2

2. Just save their HTML File with the file name they provide and then upload it onto your server. Now select Verify in "Webmasters Tool".

Similarly you can also verify your blogs and websites with Yahoo too.

PS: Verifying Blogs need some trick.

For HubPages no need to verification.

In case to verify your personal website just take to code from webmaster provided and add that code in meta tag to head section of your main page and it is done.

Second way is create a simple html page and add code provided by webmaster into head section and upload html page to your website, simple isn't it.