Craft a cartography table
Open the cartography table
Place a map in the first slot
Place paper in the second slot
Take the enlarged map
Repeat with the enlarged map and more paper to make it bigger again
Use the map while exploring to fill in more of the world
Keep the map centered on the area you want to show
Make multiple adjacent maps if you want a larger overall map wall
Place maps in item frames to display a big map on a wall