Printing setting up

[FracturedVisual]

Hello, I'm just new to this, as I now been given printing equipment to try my own business.
First I just want to do the mug printing. The size would be a 8x3.5? I was wondering what you all use as I have Photoshop and Corel Draw X7.
Just want to know which the best to do the layout for the mug design.
I have an Epson WF 3520 printer. When I want to start printing, what the right actual setting to use for layout for the correct size that actually fit onto mug.

There might be an answer somewhere on the net, but I might of missed it out. But hopefully to get some help from you guys.

Many thanks.

Elliott