How do you add a sim contact on a moto e ?

I want to add a contact as a sim contact not onto the phone itself how do I do it?

Have a look at The Moto Help app....the big blue "?" in amongst your app icons......scroll down to Calls and messaging/Phone calls......Select SIMs for calls.

I'm not sure if this can be done with the stock Contacts app, I haven't seen that option in my Moto G. Plenty of apps in the Play Store to help you to copy any contact to your SIM card though. Search for "export to SIM" and check if any of them suits your needs.

Edit. Had a second thought :) My phone came with a SIM toolkit where you can manage contacts. Take a look in your app drawer for a similar app.