Increasing Blog Preview Text

Hi guys,

Sorry I've tried to search this to see if it's been asked before, but how do you increase the length of text that shows on a blog page before you click on it? Please see here: https://oncejustadream.com/blog/ At the moment I have no text showing, it just shows the title then "... read more" so I want to show a few sentences before that.

Thanks,
Ella