Just put it in, boot and answer the questions and follow the instructions. This will return the PC to the state it was in when it left the factory (assuming it's a standard restore disk, which is most likely). Probably they did this already or the new hard disk would be empty.
Then install everything you like to get the machine in the state you want it to be. That includes installing all programs you need (such as antivirus and spyware protection) and a driver for your printer. If you can't do it yourself, find a friend or family who can or pay a shop to do it.
First, let me explain: A few months ago I bought a new laptop from Best Buy, and since (aside from installing antivirus and spyware protection programs) I didn't know what things I needed to add to a new computer, I paid Best Buy to do all those for me, and also bought a warranty plan. Some months later I encountered a problem with my laptop and brought it in, then I found out I had a bad hard drive. They were able to replace it, and I just got it back recently, but they didn't do any of the preliminary stuff they did before (i.e. installing antivirus program), but I do have the restore disk they made for me when they initially set up my laptop. Now, my question is, instead of figuring out what I need to put back into my laptop, can I just use the restore disk on it? If so, how would I go about using it (I have Widows Vista Home Basic btw). If not, then what essentials should I have on my laptop?