How to change the main font size of my paragraph on my blog pages

Hi, I am trying to change the font size of all my blog page text to size 20 or higher but even if I did that - it doesn't show when I adjust through the site design styles. Is there a custom code for this? 

Try inserting this into CUSTOM CSS:

.entry-content p
{font-size: 20px !important;
line-height: 1.6px !important;}

Thanks so much. And do you know what's the custom code if I need to increase my line height to 1.6px?

@DPruittHey, just following up on this? any idea whats the custom code if I want to also  increase my line height to 1.6px?

This code is now updated; if 1.6px is too tight, you can change it to 1.6em