Hopefully a Mod moves this thread for you to the Questions And Help section
@Fairy Dust
To gain population you can:
1) upgrade your current residences
2) build more residences
3) Place a culture building that has population added to it
4) Upgrade or build a Golden Abyss Ancient Wonder
5) Check your city to see if there is unnecessary buildings using up your population to sell off
6) Spend diamonds to buy Magical Residences to replace your normal ones
Hope this helps and Welcome to the forum