I can't seem to find the properties on the edit page of a homebrew weapon that allow the weapon to reflect its +1 bonus to hit and dmg when a character has an item equipped from their inventory.

If you are talking about +1 weapons, the modifier is "magic"

I tried to make al weapon +3 but it doesn't give the bonus when equipped to the character

Quote from resilientdm >>

I tried to make al weapon +3 but it doesn't give the bonus when equipped to the character

 Have you given the item the modifier "Bonus -> Magic" and then entered "3" as the Fixed Value?

If you have, did you mark the item as "Requires Attunement"? If so, are they attuned to the item?

If not, post the link of the item here (it does not need to be published), and I'll take a look for you. :)

I forgot I have to attune the item separately XD. That was it. Thank you very much

This was so helpful, thank you so much.