No, it is only an inhibitor, i.e. anti-corrosive properties. You should have flushed the system first, drained, flushed again and then add inhibitor, preferably with a PowerFlush (Low Pressure High Flow). Fernox is excellent choice though.
If the property will be unattended for a period over a cold spell, you should fit a Frost Stat, wired to the boiler and fit a pipe stat to the Flow Pipe from the boiler, set to 30°C. This will bring on the boiler should the temperature fall below 4°C and turn off the boiler again when the water temperature within the heating system reaches 30°C. You can of course omit the pipe stat, but in very cold weather, the boiler will keep running until the temperature surrounding the frost stat goes above 4°C.
To fit the frost stat, you will require a permanent live wired to the boiler so it can over-ride your existing system that calls in the boiler. Some boilers will have 4 core wiring, instead of 3 core, so this will be the spare. Get a qualified electrician or suitable qualified boiler engineer to check/carry out the necessary works.