Hello, and welcome.
To become a TSA Precheck approved traveler, you need to apply for the program, preferably online and then be approved after being fingerprinted and presenting official identity documents at an Enrollment Center, to complete your registration. The fee for TSA Precheck is $85.
Please see all necessary information at the following site:
Click on the necessary links, follow directions and you can start the application process.
If you do any international traveling, as well, it would be worth it, monetarily, to apply for Global Entry (GOES) instead, because it costs only $15 more than Precheck and includes the Precheck program, as well. Here is information to begin the online application for GOES, if you choose to do so:
I hope you found this answer helpful and will please take a moment to select a positive rating from the stars at the top of your page, then click 'submit;' this is the only way I will receive credit for assisting you. Thank you very much!
Even after rating, I will always be available if you need additional information; just click 'reply' and I will be glad to continue.