Can anyone help me?? its about automatic logout

Hello. You guys know how i can change the time a user have to be inactive before he/she automatic logs out?
Thank you!

To my knowledge you can't, but you can check the box "Log me on automatically at each visit" when logging in. Now you should stay logged in when refreshing the site, even if your current session ends and you became inactive. This requires cookies though and that your browser allows this for your site - check the browser options.

Thanks.
so where you find "Log me on automatically at each visit"? under what tab?

You can find this when loggin in - below the username / password forms.