What is this plant
This looks quite a bit like Avocado. They need as much full sun as you can give them, and we'd suggest repotting it with fresh potting soil. The scorch on the leaves could be a build up of salts from watering or fertilizing, or if the plant dried out or has been positioned over a heat vent.
If you can put them outside for the summer and keep it watered, it would like that.
There is a lot of good information online on how to grow avocado as a houseplant/tree, though it is unlikely that it will ever bear fruit.