Hi Julie, Welcome to WikiTree
I used the Search feature in the Find menu on the upper right. I found at least 50 William McCollums. We can help you a bit more if you have additional detail, like when and where he lived, birthdate, deathdate, children, spouses, parents.Any details you can give us will help.
You can try the Search and look at the list yourself to see if any of those Williams is the one you are looking for.