I am a little unsure on the order in which to compile application materials. I am taking my first LSAT on September 10th and will be applying ED in October. Can I purchase CAS before I have my LSAT score and LOR's submitted?

Hi everyone! I have been reading quite a few posts about difficulties with proctors. I was wondering if anyone had any advice to make sure things go smoothly on test day. I know every second of this test counts, and I would hate to lose precious time because of a miscommunication with a proctor. Thanks in advance!