Never done this on a freelander, but it can't be much different than any other vehicle I have worked on.
S-Belt before you remove it, make sure you draw out the pulley's and the route of the belt or you will regret this later.
Normally you will need a wrench or ratchet and socket of the correct size then you attach it to the tensioner pulley and turn to the right... the spring will get real tight and your will loosen the belt... remove.
Make sure you have disconnected the battery, so when you unplug the alternator and undo the wires you don't fire anything.