Hydrogen fluoride reacts with water to form an acidic solution. The chemical equation of hydrogen fluoride reacting with water is:

`HF + H_2O harr H_3O^+ + F^-`

From the equation it can be seen that the addition of hydrogen fluoride in water leads to the formation of a positive ion `H_3O^+` and `F^-` . These charged ions help in the conduction of electricity with the positively charged ions moving towards the cathode and the negatively charged ions moving towards the anode. At the cathode, the ion would absorb an electron forming water and hydrogen and at the anode the ion would give up an electron forming fluorine gas. The water solution would continue to conduct electricity forming fluorine and water in the process till there is none of the electrolyte left.

On its own, or pure water (H20) does not conduct electricity very well. That said however, when certain substances as in this case, Hydrogen Fluoride-are dissolved in water, the solution does conduct electricity.  

HF + H2O → H3O+ F –   or   HF (aq) + H2O → H3O+ (aq) + F – (aq)

Hope this helps!