It is really fairly straight forward many SSD manufactures sell upgrade kits which include SSD (go for 500 GB) appropriate USB to SATA cable and download instructions for cloning software, works best/fastest transfer if have USB 3 ports on computer but USB 2 ports work just slower.
Depending on your machine the SSD may slide right into a hard drive slot sometimes an adapter may be needed as the SSD's are smaller than standard spinning drives. I use Samsung, Crucial is good, Intel a little pricier.