I have just got a new Emirates I.D. card  which is valid for 1 year and want to add my E-gate to it. I live in Abu Dhabi. Where can I go, to have the E-Gate feature ‘added’ to my I.D. card? (My wife is getting a new card as well so I will change her card at the same time).

I presume you have Abu Dhabi residency if you live there and not Dubai. Either way it is a very simple process to add the e-gate to your ID card whether you are in Dubai or Abu Dhabi. There are many centers which will do this for you, follow the links to find out where is nearest to you

here for Abu Dhabi and here for Dubai.