Sure, go to Seller Admin > Shipping Settings, leave everything on the first screen set to 0.00 and click Next to reach the Shipping Rules screen.
There, you will create one Rule with the Shipping Rate Calculator set to Flat, with a Flat Shipping Amount of 4.00 and Max Items in Cart of 1, and click Submit to save the Rule.
Then create another Rule, this time with a Flat Shipping Amount of 0.00 and Min Items in Cart of 2, and click Submit to save that Rule.