After you sign in to your Koinim account, click on "+Deposit" button under "ACCOUNT TRANSACTIONS" headline. When you select to “Deposit Dogecoin” on the opening page, sum of letters and numbers starting with "D" in the information box is your Dogecoin wallet address. This address is defined to deposit Dogecoin to your account.
You can do this transaction by scanning data matrix on the page via your mobile phone and keep your wallet address on your smartphone. Your address is re-created automatically after every transaction.
You can sign up a new address by clicking "+Sign up a New Address" button. Re-creating time of unused current addresses are 24 hours.