A note about thread: If you are using a shirt that is not white, match your thread to your shirt color. If you can't find an exact match, go darker.
Supplies (I'm already working so my t shirt is not in the picture)
Cut and thread a strand no longer than 18". This is important, any longer and you will get tangles in your thread BAD. Any shorter and you'll spend more time then you have to re-threading.
Here you can see that I've already finished the sleeves, but it's the same method.
This kind of pearl trim is ideal because its easy to hide your stitches in the links. You can see I've already sewn a few down.
Hold the trim onto the shirt. As securely as you can. Push your needle through the t shirt and directly over a link.
Pull your needle all the way through and then put it through directly under the link you just went over.
Repeat the stitch over the same link. So each link has two stitches holding it in place. Keep working and eventually.....
And you're done! Enjoy your (semi) new t shirt!