First a freewheel and a cassette are not the same thing.

A freewheel has no lockring and can be installed with no tools as the chain force will tighten it more than sufficiently.

A cassette requires a lockring tool and a wrench as the required tightening torque is very high (40 N-m ) and you cannot possible get it anywhere near tight enough by hand.

Both types require tools to remove.