Half life 1 (Original) is that possible ? Thread

Is that possible to edit a map and add npc for campaign maps ? I would like to know how to add (not replace) but to add some females barney and fem scientist to the original game !

from what I've heard you have to unlock them first but i won't be able to tell you how cause i don't touch that honestly the only Editor I've ever touched in my life time was the Starcraft 1 Campaign Editor as well as some of Starcraft 2's Editor but not as much as Starcraft 1's