This command:
bitcoin-qt -keypool=1000

Is if you are running Bitcoin from the command line (e.g. Terminal in OS x, or a shell in Linux).

You can edit the config file to increase it, see:
https://en.bitcoin.it/wiki/Running_Bitcoin

You can see the OS x directory and file you need to edit with the keypool=1000 command.

In the wiki the example shows:
#keypool=100

which means it is commented out. You can edit it to say:
keypool=1000