The answer won't be simple, I'm afraid - making NPCs isn't simple!
As far as I know, all NPCs have a controller, which is an object which tells the game when the NPC should show up, who the NPC is (i.e. which character file to use for the NPC), and what they do. Some controllers are invisible, like Mrs Crumplebottom's, while some controllers are visible, like cash registers which create cashier NPCs on community lots.
If you want to make your own, the easiest way is to clone a different CC NPC, for example Echo's Easter Bunny or Carnival Clown. You'd need to clone the object, and also clone the NPC, and link the cloned NPC to the cloned object - then make whatever changes you want, to the NPC's appearance and to the BHAVs that control what they do.
This isn't really a beginner project! If you've read this post and thought "okay, I don't know exactly what to do but I understand the general approach", then I reckon you should be able to succeed. But, if you've read this post and thought "What??? None of this makes sense!!" then you probably need more experience with making objects and BHAV mods before you can start working on a custom NPC.
What I lack in decorum, I make up for with an absence of tact.