How to set/change a trigger of an automation flow
Automations/Flows always start with a trigger.
Automations, flows and workflows can all be used interchangeably, they're all referring to the same part of the platform, but everyone has their own preferred name for it.
On the workflow/automation canvas, at the top, middle of the screen, you'll see a rectangular box that says "Add New Workflow Trigger".
When you click on that, a menu will slide in from the right asking for the "Workflow Trigger Type".
You can also choose to rename your Workflow trigger too.
You can add multiple workflow triggers, and when any of those occur, the workflow will trigger.
Once you've built out your triggers, and the workflow itself, you can come back here and choose the default start step, and go into more advanced options, such as if a user is already in a flow, restart them at a different step.
There are filters on the workflow triggers, but you may find yourself using the "Condition" step in flows, as it dynamically adds more filter options.
Most people will just click on the "Add New Workflow Trigger" and choose which triggers they want to use, which in most cases, will be a form submission or tag.