1) Log into postgres
psql -U <DB_USERNAME>
2) After you are connected, switch to the DB you want to install the extension for:
3) Then install the extension as answered previously:
CREATE EXTENSION pg_trgm;
Installing the extension initially gave me issues because I was not doing step 2. I thought the installation was a global ...
Managed to resolve the problem, I was using an md5 sum of my Postgres password in the user list. I did this because I saw it in 3 different guides but upon looking at the official docs I saw you need to put your password in plain text while having the auth type still md5. This makes sense now but why 3 different guides on different sites all gave wrong info ...