The Hohmann Transfer is clear enough; Accelerate on your (circular) orbit at the right time, raising the apoapsis until it meets the target orbit. Once there, burn again to raise the periapsis - matching the target orbit, and as result speed of your target. If you picked the moment right, you're really close to the target, and ready for final approach and proximity operations. The only really tricky part is finding the right moment to start, so that the moment you're at your new periapsis the target is there too.
Now, how is the orbital transfer performed if raising the apoapsis can't be easily done in one short, neat burn? Say, you use a ion engine that will need two hours to create the delta-v necessary for the Hohmann transfer orbit, and your whole orbital period currently is forty minutes?