Answer by taking a quote from the following article:

Cable (Nathan Summers) is a fictional character appearing in American comic books published by Marvel Comics, commonly in association with X-Force and the X-Men. The character first appeared as a newborn infant in Uncanny X-Men #201 (Jan. 1986) created by writer Chris Claremont, while Cable's adult identity was created by writer Louise Simonson and artist/co-writer Rob Liefeld, and first appeared in The New Mutants #87 (March 1990). Nathan Summers is the biological son of the X-Men member Cyclops (Scott Summers) and Madelyne Pryor (Jean Grey's clone), the "half" brother of Rachel Summers and Nate Grey, and the genetic template for Stryfe. He is from a possible future timeline, having been transported as an infant to the future, where he grew into a warrior, before returning to the present.

Nathan Christopher Charles Summers is the son of Scott Summers (aka Cyclops), and Madeline Pryor (who was later revealed to be a clone of Jean Grey). Writer Chris Claremont, who had written the series since issue #94 (August 1975), revealed Madeline to be pregnant in X-Men/Alpha Flight #1 (December 1985). The next depiction of her pregnancy was in The Uncanny X-Men #200, when she goes into premature labor. In the following issue, #201 (January 1986), Nathan first appears as a newborn infant.  The character's first appearance as the adult warrior Cable was at the end of The New Mutants #86 (Feb. 1990). He does not appear anywhere in the issue's story, but the "next issue" teaser. This was followed by a full appearance in The New Mutants #87 (March 1990). At first, Cable was not intended to be the adult version of Nathan Summers, but was created as a result of unrelated editorial concerns. Editor Bob Harras wanted to "shake things up" for the book, and felt a new leader was needed, one distinct from the perennial X-Men leader and the New Mutants' first mentor, Professor X. The book's writer, Louise Simonson, thought a military leader would be a good idea, and Harras tasked the book's artist, Rob Liefeld, to conceptualize the character. Harras may also have suggested the character's bionic eye. Both Simonson and Liefeld each separately conceived of the leader being a time traveler from the future. Liefeld chose the name Cable for the character. Liefeld explains the creation of the character:  I was given a directive to create a new leader for the New Mutants. There was no name, no description besides a 'man of action', the opposite of Xavier. I created the look, the name, much of the history of the character. After I named him Cable, Bob suggested Quinn and Louise had Commander X.  Harras and writer/artists Jim Lee and Whilce Portacio, who were writing the X-Men spinoff X-Factor that starred Cyclops and the other four original X-Men, decided that Nathan would be sent into the future and grow up to become Cable. Liefeld, who conceived of Cable and his archenemy Stryfe were one and the same, disliked this idea. (Eventually Stryfe was revealed to be a clone of Cable.) In the 1991 X-Factor storyline, Nathan is infected by the villain Apocalypse with a techno-organic virus. Because he can only be saved by the technology of the far-future, Scott reluctantly allows Sister Askani, a member of a clan of warriors dedicated to opposing Apocalypse, to take Nathan into the future so that he can be cured, a one-way trip from which she tells him she and Nathan will be unable to return.

And how did he appear?
This was followed by a full appearance in The New Mutants