You can use it like this:
Aluminium loses it's outer electrons:
These are taken in by the hydrogen ions:
In this reaction the chloride ions are spectators - they take no part in the reaction.
If you want to be able to balance the equation using oxidation states, here's how...
First you need to work out the oxidation states of each element, notice the ones that have changed, work out how many electrons they have lost/gained. From there find the key number to balance the equation and from then on this trial and error.