You are next to the Galata Tower.
In 15 min you are at the istiklal street.
You are near to all places like besiktas, cihangir,nisantasi and ortaköy.
Its easy to go there by walk or with taxi or dolmus (collective taxi).
You have also a metrostation there.
Its behind the Galata tower in a small narrow street.
You dont have an elevator.
So if your apartment is a the 4th floor you have to go upstairs and that will be a little bit closely with big luggage.
If you have questions mert will answer you very quickly.
Had a nice stay and i can recommend it to everyone.