When can you use the yeast? If it's a few days you can put it in the fridge. Or this might be a good opportunity to make a yeast starter (which is recommended anyways) if you plan on brewing in the next day or two.
Good judgement comes from experience, experience comes from bad judgement.
No, you can put it in the refrigerator until it is time to brew or better - make a starter for your brew day. Look up starters. The pack will ferment a batch but you should pitch the proper amount of yeast for your batch.