If you have a high bp, does it mean you have a enlarged heart?

High BP. Untreated and longstanding high BP can cause your heart to "enlarge" - both in thickness of heart muscle and also dilatation of the ventricle and atria. Keep BP less than 140/90 and you can prevent heart failure.
It can do that. Long standing hypertension can cause hypertrophy of your heart which means thickening of the muscle and enlargement.