I'm sure someone has a very detailed list of things but I usually plan an hour for travel time no matter from where to where.
For Magic Kingdom to Epcot, you will need to take the monorail from the Magic Kingdom to the Transportation and Ticket Center. If you have to wait the full length of a monorail, it could be twenty minutes before you even board that monorail. Then, at the Transportation and Ticket Center, you need to transfer to an Epcot monorail and if you have to wait a full cycle, it could be another twenty minutes until you board that monorail.
Or, you could take the ferry boat from Magic Kingdom to the Transportation and Ticket Center and then the monorail from there, again with the wait times at the max.
Or, you could get on a bus from the Magic Kingdom to any of the Epcot resorts (Yacht/Beach Club, Dolphin/Swan, Boardwalk) and then walk from there to the International Gateway and enter Epcot or take a Friendship Boat to the International Gateway. Same wait times as usual.
You said you are a first timer so I'm pointing out that there are many different ways to use Disney transportation to get from point A to point B and that's why I use an hour as a guide.