if your trying to align everything in your forum to the right or left your going to need to access your admin control panel and your themes templates otherwise you will only align items in your posts if using the mycode align
To align everything left or right in your forums follow these steps
ACP > Template & Styles > Themes > {YourTheme} > Global.css
after accessing the global.css you will need to find the body of your forums usually located at the very bottom of the quick selection tool in the editor, after finding the body you will then type this code on the right for the extra css
text-align:left;
or
text-align:right;