You've to generate addresses each time, and then they aren't shown again. So, if you wish to receive coins, simply generate address (either manually or programmatically) and then send coins to it, you'll have to do this every time. You won't be able to see your generated addresses to avoid false transactions as explained in the following scenario: As our API involves generation of addresses for each transaction and a callback URL. If we show the addresses and then you send coins to an existing address, we may inform your callback URL (for the generated address) and then this may cause troubles at your site. Therefore, you're clearly recommended to generate new addresses every-time, or keep a record of existing ones.

ADDITION:

All your generated addresses are monitored, while you won't be able to see them, but they are always monitored for transactions.