We recently revised our Growing Apple and Pear Trees in a Home Garden web page, which includes care information like pruning and potential pest/disease problems common to apples in general. Columnar cultivars have so little branching that you won't have to worry about most of the pruning tips on that page, but still will need to manage the tree yearly to prevent a pest or disease outbreak that might ruin a harvest.

Since it sounds like you may have only one tree, you can verify from the tag or catalog information if the apple you chose can self-pollinate. Not many apples can, which means they would need a second cultivar to cross-pollinate with in order to fruit.

Miri