Hi Barry,
Star Magnolias are beautiful trees.  They require for best results slightly acidic soil between 5.5 - 6.5.  They can tolerate a lower more acidic soil to 4.5.  
You can purchase a pH test kit at most local garden stores.  Test the soil you are going to plant the tree in.  You can add powdered sulfur to the soil hole, mix it in to reduce the pH if needed.  They like moist soil that is rich in nutrients.  You can add composted manure to enrich the soil.  Once planted you can add composted manure annually around the base of the tree.
The hole for the tree should be the same depth as the root ball so the trunk when filled in comes to the same height as it was in the pot.  However, you should make the hole twice as wide as the diameter of the root ball.  This allows the roots to spread out.  If the tree is root bound, more roots than soil, gently pull the roots out and lay them flat in the hold.  If you leave them, they will continue to grow in a circle.  
These trees are relatively free of issues.  Keep the branches uncrowded for good airflow and look for scales (an insect that covers itself with a hard shell and sucks leaves and branches.
I am adding a link for Start Magnolia, general info:
https://www.thespruce.com/star-magnolia-trees-2132137

Scale insects

They can be removed physically with a dull butter knife.  However, they can cover limbs quickly so check the tree once a month for them.  Once they form a hard cover, insecticides will not work.  
If you have further questions, please recontact us.  Thank you.