I would wash it on cold on the gentlest cycle you have and then I would fluff it only in a cold dryer and then take it out and hang it on a hanger, pulling the sleeves, collar and body of the T-Shirt straight. Will probably need a light iron (or steaming).
If that makes you nervous then I would wash it in low suds by hand in cold water, rinse it gently to get the soap out and then gently roll the item and squeeze the water out over and over again (never twist and wring the fabric). Hang it over your bathtub or in your shower until it stops dripping and then transfer it somewhere to continue drying. As it's drying, pull the sleeves, collar and body to shape it so the wrinkles lessen.
Good luck...
*~"Never eat more than you can lift......" Miss Piggy~*