Help syncing email through iMap

Hi please help if you can!

I have a new iPhone 6 Plus after putting my old one through the washing machine last night! yep I left it in the pocket of my jumper! Anyway all sorted today and have the new one here. I have set it up as a new phone and then restored it from back up in my iTunes. That's all working well. The problem I have now is the following.

I have paid someone to set up the emails on my iMac and the email on my iPhone to sync through iMap. This meant if I deleted an email from my phone it would delete on my computer and if I delete an email on my computer it would delete on my phone.

I do not know for the life of me how to set this up again. I really do not want to pay someone again to do this and would much rather learn for the future. If anyone is able to assist it would be really appreciated.

Thankyou
Tracey