Okay....if you're at...
MK...you take either the monorail or ferry over to the TTC. From there you monorail to Epcot, or take a bus to DHS or AK.
Epcot?? Monorail to TTC to get to MK, boat, bus, or walk to DHS, bus to AK.
AK?? Bus to Epcot, DHS, and to TTC for MK
DHS??? Bus to Epcot or walk or boat, bus to TTC for MK, bus to AK.
When at Epcot...if you're in the WS area, and you want to get to DHS??? Head out the back door (International Gateway) and boat (about 25 mins, not counting wait time), or walk (about 20 mins) to DHS. Buses run to AK and DHS from the front of Epcot.
Hope that helps a bit.