Most cruisers enter the ICW just below Norfolk, VA. It's a great trip and a very relaxed and scenic way to get to FL.
Your trip from Portsmouth to Norfolk will be the most demanding part of your trip. You can make long offshore passages that will quickly bring you to Norfolk or you can take your time and make the trip in short hops.
Given your stated level of experience, I'd suggest traveling slowly at first until you get your sea legs and get to know your boat better. Don't be in a hurry! This trip is going to be a perpetual "Kodak Moment", so enjoy yourself. Make sure you've got lots of time and set no deadlines for yourself. Wait for the right weather and if it's questionable, stay put.
If you choose the short hop method, your longest offshore stretch will be the coast of New Jersey. You will have to do some overnight sailing here, as other than Atlantic City and Cape May, there aren't any practical places for you to duck into once you've left Sandy Hook.
From Cape May, you've got a choice; continue offshore to Norfolk or head up the Delaware River to the C&D Canal. This route will connect you to the northern end of Chesapeake Bay.
Personally, I loved Chesapeake Bay (other than the stinging jellyfish!) when I passed through on my way south back in 1999. If you've got the time, I recommend you take this route. I liken Chesapeake Bay to a Thomas' English muffin, with "lots of nooks and crannies" to explore. You could spend years cruising the Bay and not see it all.
Once you reach Norfolk, you'll have a choice of ICW routes; the eastern route through Virginia Cut, or the western route through the Dismal Swamp Canal. The draft of your vessel may require you to choose one over the other. We chose to take the Canal route to Elizabeth City and absolutely loved it. Read your cruising guides and reports from other cruisers to help you make a decision.
As far as traveling the ICW goes, watch your depths, stay in the marked channels, and expect to bump bottom from time to time. Also, plan to motor most of the time. Skipper Bob's ICW cruising guides are very highly-rated by cruisers and you should have these aboard.
You're going to embark upon a great adventure. Have fun and be safe!