You can do this a couple of ways:
1. Measure an existing shirt that you already own – that fits you exactly the way you like.
2. Have a friend/spouse/significant other help you. The “Measure Tab” shows exactly how to measure for a custom-sized shirt.
3. Go to a tailor, and have him/her measure you. They may do this for free, or there might be a slight charge of $5 for this service. Make sure you write down all the different measurements you may need.
4. DIY (Do it yourself). This is not the optimal way to do this, but you can pull it off. Make sure you pay attention to the measuring guide located under the “Measure Tab”.