Automating Email Alerts based on Custom Due Date field

[John]

I am looking to set up a rule to have emails sent to the assignee based on my TBX's approaching their Due Date. Due Date is a custom field we use. I am new to Automation and this may be simple, but I didn't see any way to add this. 

[Mauricio Heberle]

What would be "TBX"? How close to duedate you 'd want this to be?

[John]

TBX is just an issue type we made. It tracks items that we need. TBX = To Be XXXX. 

I would want notifications sent out to assignees as we approach the due date, probably 45,30,15 days from due date. 

[Mauricio Heberle]

Your automation will look like this:

[John]

Thank you!