Before you start to grow your account or the account of your client, you need to know the product or the service your selling or your client is selling. You need to add relevant people. If you're a lawyer or your client is a lawyer selling coaching or other services, you need to add people that is in the same niche.
How to Increase Facebook Engagement in 2022 :
https://www.youtube.com/watch?v=Bam_rXmoOs4
Open Facebook

Click on friends

Start to add people in the suggested section
Get to 5k friends and turn your account into a page
That's it! You know how to growth hack your Facebook account.