Soak the root area well and then let it just dry out before watering again. Poke your finger or a small stick a few inches into the soil to see if it's wet or not. Over watering can be just as bad as under watering.
Check the root ball, not the surrounding soil, it will dry out sooner. Use a finger or stick to poke a couple inches into he ball, to check for moisture.
The tree will spend some time establishing new roots first, don't expect them to take off immediately.
Use some composted manure, available at garden centers for a couple bucks a bag, to add organic matter to the surface and supply all the fertilizer needed. The bag has instructions for application rates. Just spread it out on the surface. Repeat annually.
Then top dress with a thin layer of decorative wood chips, which will break down over time into compost, help moderate soil temperatures, and help hold soil moisture. Total added compost and wood chips should be no deeper than about 2".
You want your chip bed to extend out a bit farther than the drip line of the tree. If the bed is too small, it won't invite new roots to grow outward.
