If they're Mesembryanthemum, I don't think they set seed (not in UK anyway)!

They do indeed set seeds and a relatively easy to grow. Wait until the seed pods dry out on the plant before harvesting them.

Ooops . . .

I just deadhead mine regularly and save the complete head in an envelope, come springtime scatter the dried heads in a tray of compost, you end up with hundreds of seedlings, easypeasy, I love them....