Good apps for telescope? ?

Stellarium will show you what is in the sky now, once you've set it up for your location.  It's essentially a star map that will move round as the Earth moves - as you will find, if you keep looking at the same thing for a while, it will move out of view, so you want something that will show what's in YOUR sky NOW.  And it's free to download.

For what's coming, you need an astronomy magazine.

Astronomy magazine always has articles on what and where  to look for things in the night sky.  Astronomy also has articles on how to get the best use of a telescope.The January issue includes star maps for the four seasons.  You can use the constellation of Orion to navigate.  To our left of Betegeuse you can find Procyon (Canis Minor).  Go a little further left and the two parallel liners are Gemini.  Go to Bellatrix (Orion's shoulder) and to our right the red star is Aldebaran (Taurus).   The head of Eridanus is immediately to our right of Rigel and our left of Saif, Orion's other foot, the bright star is Sirius (Canis Major)  

Sky & Telescope Magazine on line https://www.skyandtelescope.com/observing/this-wee...

https://www.skyandtelescope.com/sky-and-stargazing...

or www.heavens-above.com

Phone apps:

https://www.inverse.com/article/47478-5-apps-for-h...

https://www.forbes.com/sites/jesseshanahan/2018/05...

https://play.google.com/store/apps/details?id=com....

https://apps.apple.com/us/app/star-chart/id3455426...

That is all that can be suggested with no clue on what "telescope" model and brand your son got.

Most Xmas ones are too small, too flimsy a support, and with too much magnification to be anything but frustrating.  Any telescope costing less than $300 will be a discouragement rather than a help.

A good idea is to seek advice at a planetarium or college with Astronomy instructor, the library for a reference book, or on line searches for best telescopes for amateur astronomy, and how to use them.

I like Sky Guide.

Not directly related to a telescope, but great for sky viewing. Hold up your cell phone and it shows you an image of the sky that you would see behind the phone, but brighter and with labels on stars, etc. 

Star Space Telescope is good. Also, read this article for other good telescope apps:

https://www.easytechtrick.org/telescope-apps/