Hard to say without seeing it. My guess is:
1. Temper your chocolate
2. Polish the inside of your metal mould with cotton wool
3. Smear a thin layer of tempered chocolate on the inside of the mould using your finger
4. Let it set
5a (if the mould has an opening when two sides are clipped together): Clip the mould together and pour tempered chocolate into the mould - fill it up and then tip it out of the opening
5b (if the mould is completely closed when clipped together): put some tempered chocolate in one side and clip the mould together. Then slowly move the mould around in a circular motion to keep the chocolate moving inside to form an even and thick coating of chocolate.
6. Let it cool. If your mould is making a good sized egg, it might be best to give it a while in the fridge (maybe 5-10 minutes).
7. Unmould. It doesn't matter if you wait too long to unmould, but it will matter if you're too quick and this just comes from experience - knowing your chocolate, mould and conditions. Without knowing your mould, I would say give it 15 mins in the fridge and see if it releases easily from the mould. If not, give it a bit longer.
Good luck - 3D moulds are a piece of cake once you've done it once or twice and can produce some great things for Easter.