Carol Danvers' first appearance – Marvel-Super-Heroes issue #13 March, 1968
A long time before Carol Danvers became Captain Marvel or even Ms. Marvel, she was simply an ordinary human. In fact, 9 years passed from Carol Danvers' first appearance in comic books in Marvel-Super-Heroes issue #13, which was published in March 1968, until her debut as Ms. Marvel in 1977.
Carol Danvers is the chief of security at Cape Canaveral, a NASA base. She may not be a superhero, but Carol Danvers achieved a lot on her own by hard work and breaking social conventions. Whether it is intentional or not, you can look at her as a representation of other women during her time.
And now to the issue itself. Carol Danvers is just a side character in Captain Mar-Vell's show. Captain Mar-Vell is pretending to be Dr. Walter Lawson, an expert on missile guiding systems. The real Lawson was killed accidently by Captain Mar-Vell's commander, Colonel Yon-Rogg, who was trying to kill Captain Mar-Vell himself. Yon-Rogg wants to kill Captain Mar-Vell so he can get the Captain's lover, Medic Una. Captain Mar-Vell works at the Cape and evaluates human technology. General Bridges arrives and takes Mar-Vell/Lawson to a secret and guarded area in which they keep the Sentry, a Kree robot believed to be destroyed. Mar-Vell tried to find a way into this area, but failed because of the heavy security.
And at the head of the security stands Carol Danvers. We meet her for the first time telling the General that she advised him not to bring Lawson into this secret area, and of course, she is very right. Her first physical appearance is also interesting. She looks like a strong independent woman, not wearing a dress, but pants. Carol acts like she's authoritative, but as we see, she doesn't have real authority. The General went against her good advice and not for the first time.
General Bridges introduces Carol Danvers with these words: "Dr. Lawson, this is Miss Danvers! Man or Woman, she's the finest head of security a missile base could want!" what does this mean? No tokenism. She was hired because she is the best person for the job, regardless of her gender. And the General manages to respect her while not listening to her advice at the same time.
Lawson wants to start working on the robot (Sentry) as soon as possible. However, Carol informs him that all of his documents are being examined by her security division because of Lawson's reclusive and eccentric reputation (the round suitcase that Mar-Vell carries with him only adds to this reputation).
The General tells Carol to leave Lawson alone. However, that doesn't stop her from suspecting that Lawson is hiding something, and she is absolutely right.
Colonel Yon-Rogg sees the Sentry through Mar-Vell's and wakes it up, hoping that it will kill Captain Mar-Vell. That makes Carol Danvers right in more way then one. If Mar-Vell wouldn't have seen the Sentry, Yon-Rogg wouldn't see it as well, and wouldn't wake him; thus preventing the damage caused to the base. General Bridges sees the destruction the Sentry is causing and he wants jets and Lawson to help neutralize it. Lawson puts on his Kree suit and flies off to face the threat. We find out that he is there to study the planet and decide its fate, life or death.
That's Carol Danvers first appearance. It's a very small role. We simply know what she does, that she's smart, but her smart advice is ignored.