Cheap 2.4GHz Antenna Tuning
The antenna design already includes a matching network. If you need to adjust it, you would fiddle with some of the dimensions given in the design. If you don't know how to do that, just leave it well enough alone.

Adding a second lumped-component matching network would probably add more problems than it would solve, and lead to greater losses than living with whatever mismatch you end up with by using the design as-is.