there are many different ways to play tabletop roleplaying games like D&D, and all use your imagination to some extent. some may just have the game master with a lose idea about the sort of adventure and characters the group will meet, as preparation, and then, everything from then is voice and dice, while others may thoroughly use the rule book, make maps, or even models of buildings, and use miniatures to represent the player's characters within the game. i personaly think the book is good to have, but only as a guideline: a good game master will make better calls than set in stone rules.

in general, the players are tasked with imagining/creating a character, with different skills, genders, items, personalities, feats, races ETC. then the game master starts telling the players about the world around them, and where they are. the players are then tasked with stating how their characters act and react to the world the GM presents. from there it can be focused on a colaborative storytelling excercise, with tales of extrordinary things happening sprinkled in, or it can be more focused on overcoming massive challenges.
if you use visual aids or not, you still use your imagination, while following the rules of the game-(book), as enforced or ignored by the GM.