Basic design intro for a novice

I would like to get started as a independent contractor by designing and setting up a small business network. After the design, I know I am to get my IP addresses from a company like Network Solutions to get on the internet, but what info would I provide them to get the appropriate IP’s to assign to the devices. If I was to design a intranet how wold I assign IP addressing to this scheme. Is there any info I can study solve these questions?