Well on firefox/chrome extensions you can search for text expander and choose an extension that works for you.
Or if you are using a phone you can do the same on the app store and I think there should be a few options.
Once you download one of them it should give instructions on how to use it, but in general it asks you to create a phrase that you want to be automatically triggered and a shorter phrase that automatically replaced with the longer phrase.
For example-
long phrase: The quick brown fox jumped over the moon.
short phrase: /qfox
and every time you typed /qfox it would replace it with "The quick brown fox jumped over the moon."