ing

It may be easier to understand if you were to put a comma after "learned," "using what you have learned, make a sentence."

"Ing" is used to make the gerund, "using." It's a non-finite verb form.

Does this make it easier to understand, Hesam?

Using the things you have learned [from the teacher/in today's lesson/...] make/write a sentence of your own.

Using a pencil and paper, write your name.

Using an eraser, erase what you have just written on the paper. [your name]