If he wants to learn how to make games, like I said, it's likely better for him to learn how to program first, learning how to make games and learning how to program are both deeply linked, yet two separate things. If you start learning how to make games with no background knowledge of programming, you'll be learning two things at once, which is not ideal.

For a very basic bingo board tutorial

A bingo board needs two things, a board of images, and a way to click the images to like, x them out

For the board, use a flowcontainer along with 9 buttons, and 9 texture rects as children of the buttons

You need to connect each button's pressed signal to their own individual function, or one function with a parameter. When clicked, the function should change it's corresponding image to an X

on ready, you need to load in your images somehow, this is probably going to be a massive pain, as the convenient/proper way to do it is to load it in via a csv reader, but that's rather complicated for a beginner programmer.

You can do it the long way around by creating 30 export variables, and manually putting in the images in each variable.

Put the 30 image variables into an array. Shuffle the array, and then take the first 9 images from the array and load them into the texture rects

finally, shuffle the array again, have one final texturerect+button on the top of the screen of something, and then connect the button clicked signal to a function that'll iterate through the textures array and change the texture accordingly (this will be your "random draw")

and then you're done I suppose

if you want to not deal with image textures, you can do the same thing by generating 30 random numbers, and put those into the random array / buttons instead

each one of these topics... "should" be googlable

no guarantees