Using Excerpts On The Main Page Instead Of Full Articles

I’m using the Aquablock theme for my blog at https://www.reidaboutit.com. I know about the “More” function, but is there a way I can set my blog to only display the “Excerpt” on the main page? “More” is fine, but I’d rather be able to write a separate teaser for the article rather than being forced to just use the first few words. Thanks in advance!