Wait until they finish flowering and the stems drop off easily, then store the corms in dry compost in a frost-free place until spring. Don't forget to label them! Then start them off in a tray or pots.

I agree with flag, but make sure the short roots are absolutely dry before you store them.
I alway`s dry mine on the kitchen windowsill in a dish
turning when necessary to make sure all over is dried out. then store them in brown paper bags in my bedroom cupboard. works well.