Cut the socks off just above the heal, right along the seam if there is on.
Turn the sock and the shirt inside-out. Put your index and middle fingers inside the sock to stretch it out and around the sleeve. My shirt was larger than the sock so I had to make sure to keep the sock stretched while trying to baste them which was kind of difficult but can be done.
I wish I would have used a different color of thread to show you how I basted the two together but I had white handy :-/ woops! Anywho, here's a photo of that and you can sort of see where I tacked them. Also, do not tie off the end when finished basting, you need it to be free floating to accomodate the stretch of the sock.
I chose to stitch from the outside so I could see where my finished seam would be and I *did* do this in black just for you to see. ;-) While sewing be careful to make sure you are only stitching one layer each of sock and shirt, trust me on this one. Also, since my sock was smaller than the sleeve it created a ruffle below my stitch. To remedy this I just stretched out the sock until it lay fairly flat.
Repeat on the other sleeve. TA-DA!! A long sleeved St. Partick's Day shirt!
I have other ideas to decorate the front so keep an eye out for the finished project.