If you have access to the SSH command line then the best (easiest) option would be to login and run the second command. You’ll need to ask your host if you can have SSH access.

find ./ -type d -exec chmod 755 {} \; && find ./ -type f -exec chmod 644 {} \;

You can also set the permissions via FTP by chmod 777 on these directories:
* magento/app/etc
* magento/media
* magento/var
* magento/var/.htaccess

If you installed sample data you’ll need to chmod 777 any files in magento/media also.

Again if you’re having trouble it’s probably best to ask your webhost who can set these permissions directly for you.

Hope this helps, ask if you need anything else.

Stefan