You need to leave then to settle in for a few days before you start to handle them. Guinea pigs are prey animals and don’t like being picked up, or touched, so you need to take things very slowly. The best way to start is by offering food from your hand. They probably won’t take it at first, but over time they will start to trust you. It’s not something you can force though.
You say you have bought a big cage - do check the measurements are good enough. Some commercial pet store cages are not big enough. Two piggies require a minimum of 120cm x 60cm (this is the RSPCA welfare standard) but the more space you can give them the better. It is recommended that if your piggies are boys, that the cage is bigger than that minimum standard as lack of space can cause fall outs.
Keeping them warm, lots of hidey houses (ones made of fleece are good for helping to keep them warm), lots of hay to snuggle into (they need to eat a lot of hay anyway, so you will need to keep lot in stock) and maybe some snugglesafe microwave heat pads as they provide an area of extra warmth if it is needed. Guinea pigs ideally need to be kept between 18/20 degrees to be most comfortable.
I have added in a link below which will take you to a selection of guides. They are the most useful guides for new owners and cover topics such as how to settle then in, feeding, handling, the importance of weighing them weekly etc.
As they are pet store piggies, it is also a good idea for you to double check the sex of them yourself to ensure you do have two of the same sex. Hopefully they are, but pet store missexing does happen.
We’d love to hear more about your piggies and see some pictures!
New Owners' Most Helpful How-To Guides and Information