Unless the pod was ripe when you were given it you may not be able to. Once ripe a poppy seed pod acts like a pepper shaker and the seed flies out every time the wind blows. I can only suggest you keep the pod somewhere cool and dry and see if the seed actually matures. If it does mature it will come out of the little 'holes' at the top of the pod. Poppy seed is incredibly fine so you will need to gather carefully to sow.

It looks brown so you may have lost them already. Have a look below the little castellated part at the top. If there is a row of little holes the pod is ripe and the seeds may have gone. I would put it in an envelope and tap it and shake it a bit. If its ripe and still has seeds they will fall out into the envelope. If there are no holes yet just keep it dry as MG says and wait for nature to do its thing. If you try to open the pod yourself before then the seeds will not be ripe.