Yes, you can build your pc and add your GPU and optical drive when they arrive because they are annyways the parts which you put in last. So this is the order in which i'm building a PC: first install the CPU, the memory and the cooler on the motherboard and then place the motherboard in the case at its place, then place the PSU, your HDD and then the GPU and the optical drive. I'we also found a walkthrough for you on how to build a pc http://www.youtube.com/watch?v=qMRvz_IYSgM
(skip to 14:00 for the actual build walkthrough). I hope I helped you!