You can do this in several ways. Here is what I do:
1) Allow students to take turns (unless working individually) selecting letter cards from a container. They say the letter, then find it on their page, and highlight it. (Use highlighters, markers, crayons, bingo blotters, or whatever you have on hand).
(Same instructions go for numbers page).
2) Call out the name of a letter or letter sound, and have them find it on their page and highlight it.
(Same instructions go for numbers page)
You could also just make a few copies of these, laminate them, and use them in a center, using dry erase markers.
I have many of these, but chose to sell them all individually for cheaper. This one is on a Clifford the Dog template. Students can color their page upon completion if you wish.
Product includes 4 pages :
1) Upper and Lower case mixed letters
2) Numbers 1-20
3) Uppercase Letters
4) Lowercase Letters
If interested, letter/number cards are available in my store.