However if you cannot get tags at the holding of birth sorted (and you may need to move these lambs soon for welfare reasons), as you will need to apply for a flock number any way once you keep sheep on your holding, and then you can tag the sheep with either your own flock number (and note the circumstances in your log book), or if you can get a couple of red tags specifically for these lambs then that's better.
It will take a while for you to understand tagging, but it isn't overcomplicated just different for new sheep keepers.