Follow the main A12 road from London to just north of Colchester, then take the A120 to Harwich. From Norwich you take the A140 to north of Ipswich, then the A45 bypass round Ipswich, the A137 to Manningtree, and from there follow signs to Harwich.
Regular services run between Harwich and London, and several other towns in the UK.
By Rail Trains run from London Liverpool Street station to Harwich International. Local rail services arrive at the terminal building, where an escalator will take you directly to the check in point.