Hello
@Stardust505 and welcome to the forum! There are no obvious questions here, so feel free to ask whatever you like. To add the trait you need, you will have to 'cheat' a bit (no mods, don't worry)
You will need press CTR+SHIFT+C to bring console up. (will be a white box that will appear in the top left corner of the screen)
Enter testingcheats true. (exactly as written)
Enter cas.fulleditmode (this enables you to make full edits, like when you start a new game)
Now click on a sim while holding the shift key down. You should get an Edit in CAS option.
Click that option and you're ready to edit your sim.
Carl has many great tips on cheats etc.. that might interest you. Just follow this link
http://www.carls-sims-4-guide.com/cheats.php