When you're working in a Task Queue, you can access Email Templates and Sequences using these instructions.
Here's how to find Email Templates from inside a Contact Record view in Hubspot. This is the view you will see when you're working a HubSpot Task Queue.
Check out this video in full screen: https://share.vidyard.com/watch/cGtgF49NcnxFqxejNtQAee?
Note if you're on HubSpot Free, you only get a few Email Templates. You get more as you upgrade your Sales Licence.