Is your problem going to be recurring? I guess it's OK if you skip the first lab... no biggie.. it's probably all admin/orientation anyway... but if you still need to change it, send an email to the tutor in charge of QMA, or drop by their office in the John Goodsell building.
EDIT: I just tried accessing the tutorials via the TAS program and it works... it seems that you still can change your lab tutorials. Here's a
link to the program if you need it.