you must breed a swinub or a piloswine because to learn ancient power it is a breeding move. once swinub evolves to piloswine you can go to a move tutor and give him a heart scale to have him teach your piloswine ancient power. when you have not raised your swinub/piloswone from an egg ancient power will not be an option however if it was an egg at one time ancient power will be an option. this is kind of an annoying process i know but mamoswine is super powerful for an ice type and totally worth it. and then you can trade it with other versions you have as long as its the right generation.