Use this CSS code: 

#wpforo #wpforo-wrap .wpforo-post .wpforo-post-content p {
    margin-bottom:  ***20px***;
}

The red-marked value can be changed as you like.

I tried this and it did not change the spacing between paragraphs, it just changed the spacing between the letters it seems. Is there a way to simply make the space between the paragraphs bigger?

add this to custom css
Dashboard > wpForo > Settings > Colors & Styles > Custom CSS

#wpforo #wpforo-wrap .wpforo-post-content {
 letter-spacing: 2px;
}

replace the 2px with the value you want

How do I increase the space between paragraphs in posts? I think it would feel more readable if there was more space between each paragraph, it feels a bit tight for me as it is now. Posting example of what it looks like.