Its really easy to make a magic square: one where the horizontal totals and the vertical totals all add up to the same number. For example, here is a 5×5 magic square:
How to build one such magic square? You could build a 3×3, or a 7×7 one for example. The rules:
1. Start with writing 1 in the middle square
2. Keep moving diagonally upwards, increasing the number by 1 each time
3. If you move out of the square, roll over
4. If you hit a square already filled, move vertically downwards one square and keep moving
All the best!