I uploaded it to the root directory of my web site(my host is UNIX server)and installed it from my browser http://mydomain.com/xoops,so XOOPS located in that directory .How can I let XOOPS be my home page and access directly it by http://mydomain.com.Thank very much!

I think you would have re-install it again directly into your public_html directory.

No, that's not necessary. All you have to do is move the files from the html/ folder (including all subfolders and files, ie. the whole site) to the root folder, and adjust the settings in mainfile.php.
As a safety precaution, copy the files in your first attempt, not move them, and then change your mainfile.php settings to reflect the new paths. Make sure you set the CHMOD rights to the cache/ uploads/ and templates_c/ folders correctly (777 or 755, depending on your server setup).

After you've done that, login as admin and 'update' the system module. This will tell the system to use the new path.

Once you got that working, you can remove the html/ folder with all the old (and now unused) files.

For maximum compatibility, leave the html/ folder empty, create an index.html file that redirects to the root path, so anyone linking to the html/ folder will be redirected to your new site address.

Herko

Maybe I can use the system functions of donaim services of my host server to do that? I mean that redirecting function.Thanks,Herko.

Google for 'meta redirect' and you'll find an easy way of doing this

Herko