How do I change Time Machine hard drive

Hello can someone please tell me how I change my time machine hard drive. when I got my new imac I also got a 500 GB maxtor external drive for time machine and now I have a new 1TB maxtor HD and I would like to use this drive instead. The 500 GB drive has about 4 months worth of backups on it and I would like to transfer this to the new 1TB drive and use the smaller drive for something else .
Hope someone can help me
Cheers
Mike

Time machine preferences -> choose disk -> use for backup

Make sure the disk(partition) you want to use for the time machine is formatted with the correct file system.

Cheers ... McBie

I think it is working
Cheers
Mike

I found this today and works well

How to copy your Time Machine backups to a new larger drive | MacYourself

problem solved
Cheers
Mike