Chances are that if you’re putting on an athletic event you want to give your participants a free shirt. And odds are that if you’re giving away a free shirt, you’re trying to figure out how to set it up. And that’s probably the reason why we’re talking to each other right now. So let’s get to it.
Go into Event Setup (from your Dashboard, click the “edit” link to the right of the event name)
Click the “Custom Questions” link on the left side of the page
Under the “Select A Question” section, select the T-shirt size (dropdown) option
In the Help section feel free to add any info that may be helpful for your registrants (e.g. shirts run one size big)
Indicate whether or not the question should be required (hint: it usually is)
For extra credit, you can use the arrows on the Custom Questions page to move the question wherever you want it relative to other questions.