z.khalid,
The TO-FROM indicator will indicate whether the VOR is behind you or in front of you when the nav receiver is set to the VOR frequency and the OBS dial matches your heading.
You can either fly a radial TOwards the VOR or a radial away FROM the VOR.
Let's say you are flying towards the VOR on a radial of 90 degrees, the needle is centred and the TO flag is visible.
You are now flying the 90 degree radial to the VOR.
As you get closer to the VOR the needle will behave in an erratic manner, however, when you pass over the VOR the FROM flag will be visible.
You will now be flying the 270 degree radial FROM the VOR.
Play with the simulator I linked to and you will get the hang of it.
