What is sampling frequency in this case?
Cutoff frequency for a discrete time filter can be expressed in different ways.  It can be expressed in radians, which is mathematically useful when analyzing the transfer function in the z-domain. It can be expressed normalized to the sample rate, as it is here, which is handy because it is a simple number to work with and is not dependent on the sample rate. Or you can express it as a true frequency, which requires a sample rate and is handy because it’s the actual frequency in the implementation.
It looks like you just need to change the units in the drop down box to set the sample rate. Probably something like Hz, but I’ve never used that tool.