Need help switching to testnet on my server for asic farm

Have a Yiimp server. Everything is fine. Hashing away. 150ghs with a TFF of 2 days. No errors on the daemon either. It’s been four days and still no blocks. I understand could just be bad luck, but wanted to switch to testnet just to make sure but not quite sure how to do it.
Would greatly appreciate help.
Thanks and GO LTC GO!