I know this question was asked a long time ago but I thought I would answer for anyone having the same problem as it was something I had a problem with as well.
You have to do a Full backup and then Transaction log backups depending on the how quickly your log is growing, I have mine set to every 10 minutes to keep it low. The following you need to do because SQL will not give you the space back any other way, what SQL is doing it takes the data out but it leaves the shell there with the same size, when the log backup is done SQL writes the data to Database and it is important to know that no rollback would be possible after that.
This is the Important part and the way to shrink the Transaction log is to set the Recovery to Simple in properties, then go to Shrink File and select log file (not data) this can be quick if you have done the full backup but it can also take some time depending on a couple of things that I am not going into now, but leave it and let it finish. When this is done go back to properties and set Recovery back to full. Now just keep on doing the backups as I stated in 2nd paragraph and you would be fine and if need be you can shrink it again, it is preferable to get your log backups right so that you do not have to shrink manually but if you need to do it you can.