GWASpower calculation

Dear All,

Sorry , sounds like a stupid question but been struggling with this for a while. I am trying to do post-hoc power calculation for my GWAS using GWASpower software for quantitative trait (i know many don’t prefer post-hoc power calculation, but reviewer asked me despite clearly mentioning it in the limitations section).
Can anyone please clarify what we are supposed to enter in the effect size (heritability) box (image attached) because GWAS plink output gives only Beta, SE, CI, p values ?

BTW I do know what an “effect size” and ” heritability” mean. My confusion is whether I need to calculate “effect size/heritability” from my OWN study, or can i just use an estimate of effect size/heritabilty from previous studies ?
Also i am not sure whether we can estimate heritability from GWAS, i thought heritability came from family/twin studies.

Hope i have made myself clear .

Thank you all