Also you can mine to a specific address (this is useful if you are mining on several computers). To do so:
1. Use existing or better generate a new address.
2. Open debug console (Tools -> Debug Console) and enter:
dumpprivkey SYourSpreadCoinAddress
3. You will get your private key. Then open spreadcoin.conf or create it if it doesn't exist (D:\Users\\AppData\Roaming\SpreadCoin\spreadcoin.conf on Windows) and add the following line:
miningprivkey=YourPrivateKey
4. Restart your wallet if it was running.
In the Mining tab you will now see notification that all mined coins will go to this address.
Of course you need to generate address and get privkey on one computer and edit spreadcoin.conf on the other.