Certified GKH Gardening Expert
Most apple varieties need to cross-pollinate for good fruit set. There are a few cultivars that are self-fruitful. If the label or catalog description doesn't mention that the tree is self-fruitful or self-pollinating, plant another cultivar to be sure you have good fruit set. Some trees may be sold as "self-pollinating" or "self-fruitful." While they are able to pollinate themselves, they will produce more apples if they are cross-pollinated.
This article should help as well: https://www.gardeningknowhow.com/edible/fruits/fegen/dwarf-fruit-trees-a-planting-guide-for-fruit-trees-in-containers.htm