There is no difference between registering a trademark for an online business or an off-line (brick-and-mortar) business: you make sure the name is not in use or registered by someone else; you try to make sure the name is original and distinctive, and not generic or descriptive (since the latter are much harder to register); and once you have begun using the the name in commerce (or have firm, near-term plans--i.e. within  the next 6 months) plans to do so, you file for registration. You can file online at the U.S. Patent and Trademark Office's website, where you can also find information and instructions.Each individual product does not have to be registered separately, so long as it is in one of the categories of products you have registered. When you get the registration, each product that uses the trademarked name/logo should bear the "circle R" mark.