Step 1:
Go to Steam\steamapps\common\AoE2DE\resources\_common\drs
There will be two folders called gamedata_x1 and gamedata_x2. All real world maps are stored here. Copy any .scx file you want.

Step 2:
Go to C:\Users\(your name)\Games\Age of Empires 2 DE\76561198105203674\resources\_common\scenario
Paste the file you copied.

Step 3:
Open AoEIIDE map editor, the real world map should be on the list.