Directions from Keleti train station

You should descend the steps beside the front door and follow the signs for metro line 2 (red line). Go down the first escalator to the ticket booth and machines. You should buy regular metro tickets (350huf) and stamp them before decending the second escalator to the platform. Take the metro for three stops, in the direction of Déli palyaudvar, to Kossuth Lajos tér.
Ascend the escalator. Exit the station to the left (you will see the parliament building in front of you) and turn right. Walk straight ahead up Bathory utca. Number 17 will be about 300m away on your right.

Google maps directions