To start using Teespring, users need to register on the platform and choose a preferred payment method. They can then begin creating custom tee shirt designs using their own design software or by outsourcing the design work to freelancers. Once the designs are ready, users can log in to Teespring, upload their designs, and set up campaigns by providing titles, descriptions, and addresses. It is important to optimize the sales channels and consider marketing strategies to attract potential buyers.