Your username here MUST MATCH your XenForo username (connected to your XF license).

    Once you have registered here, then you need to start a conversation at xenforo.com w/Bob and provide the following:
    1. Your XenForo License Validation Token
    2. The Domain Name associated with the License
    NOTE: Your account will be validated once ALL requirements are verified/met. Thank you for your patience.

Change font size AMS

If you are talking about the Article Content (added via the rich text editor), then that is controlled by Core XF, not AMS.

If its not that specific text, can you post a screen shot of the specific text you are talking about so that I can see if its something that Core XF controls or AMS controls? 90+ % of the text display is controlled via core XF LESS.