If LTA forms a part of your salary, then you can avail this allowance on a trip within India with your family. This does not apply for foreign travel :(
LTA can be claimed twice in a block of four years. We are currently on the 1st Jan 2014- 31 Dec 2017 block. You can claim two journeys against your LTA within this period.
Submit all the boarding passes in case of flights, travel tickets and bills to your company. You can see the allowance you've received in your Form 16.