Answer about Vocal

Hello everyone!
With great help from this forum last week I was able to add vocals to an instrumental.
I am now trying to find out how to add harmonies. Not trying to make a prof track or anything.
Do I need to add new vocal tracks over the first one or is there a tool to make this happen… or am I trying to do something that is not possible?

Sing them. Pitch Shift software doesn’t sound right for shifting that many notes, and Harmony software may not do complex harmonies like sevenths or minors.