You may want to start by reading
The Master of Disguise by Antonio Mendez and then Spy Dust by Antonio and Jonna Mendez. Both were top CIA covert operators. In fact, they met on-the-job and are now husband and wife.
These books are real. These two have been there and done that and now they're telling just a few of the tales.
Antonio, "Tony," started at the CIA as a graphic artist. After showing special talent in his routine graphic arts work, he was recruited to become an "authenticator." In the strage vernacular of the CIA, an "authenticator" is one who forges documents. And he became an expert at it.
One of the major uses of forged documents is "exfiltration." This means getting someone out of a foreign country when that country would rather that said person not leave. The obvious need is for forged travel documents, but what you really have to forge is a whole identity. If the cover is that this man is a traveling anvil salesman, then he'd better have, in his briefcase and wallet, receipts from hotels, restaurants, rental cars, a bus schedule from one of the cities he visited, a half-pack of matches from a bar in another city he visited, not to mention anvil brochures, an order pad with orders written on it, business cards from people he met with along the way, a half-finished expense report on a form bearing his company's logo, etc., etc., etc., right down to a wadded up cocktail napkin from the airport lounge in one of the cities along his forged trip. Some of that can be collected, but someone's got to go get it. And a lot of it will have to be forged. On one of his missions, the cover story was that the man being exfiltrated was a movie producer scoutting locations for an upcoming movie. This required forging a movie script.
But, it gets better than that. Tony has to get into this foreign country undercover himself with all of his materials and equipment, meet up with the local CIA people, forge all the documents, all of the related stuff, all of the "pocket litter," teach the person being exfiltrated to BE his cover character, and then get himself out too.
Tony did this so well that he rose to become the chief of "authentication" at the CIA.
He was typically accompanied by another person who was an expert in disguises who would disguise the person being exfiltrated. Tony realized that getting two technical experts in and out didn't just double the problems, it raised them to the power of two. So, he learned to do the disguise work too.
Tony came to do this so well that he became the chief of disguise too.
In fact, Tony learned to do this "exfiltration" stuff so well that he started to lead the teams and plan the missions.
His specialty became operations in the most difficult theater at the time, Soviet Russian, Moscow, right under the KGB's noses. He was a top covert operator.
Jonna started off as an "upstairs man" doing the most difficult breaking-and-entering jobs including the theft of a top-secret cypher machine from a Russian embasy, the stuff of Bond movies.
She, eventually, also got into the disguise unit and rose to take over from Tony as chief of disguise.
These books are absolute page turners. You'll love them.
To answer your question as to how to become a top CIA covert operator, the answer is that the CIA recruits for those positions from within. You'll have to start as a flat-foot pounding the pavements of some hell-hole somewhere in the world and distinguish yourself. They're hiring right now. The base salary is $52,180.
