Templates
Manage the team's saved replies from Settings.
Settings > Templates lists every template, split into a Shared tab and a Private tab: shared templates are set up by an administrator and available to the whole team, private ones are yours alone.

Go to Settings > Templates.
Select New template.
Enter a name to find it by later, and a subject if the template should set one.
Choose whether it's shared or private, and, for a shared template, which folder it sits in.
Limit it to one mailbox using Inbox scope, if it shouldn't be offered everywhere.
Write the body, using the same formatting toolbar as the composer.
Select Save.
Insert a saved template from the formatting toolbar while composing, then edit the result as you would any other email.