As per my knowledge of Vastu Money frog are coming in 11 types and it is a Feng shui product.
first you should check with Vastu Expert then place money frog.
As general you can place Money frog in South west of your house and frogs back should be towards South.
As you know Indian Vastushatra are depend on North and Feng shui is on South.
So remember this when you want keep Feng shui products like Money frog.