Teach your horse to tie up without fidgeting.
If you have a problem with your horse fidgeting when tied you first need to look at why this is happening. The most common cause is anticipation bought about by your horse not waiting for your lead or command. With theses cases you need to establish yourself as the leader and the person who will put their horse where they would like them to be rather than the horse taking the lead. You can do this by improving your general groundwork, such as making sure you are leading your horse and not the other way round and being able to lunge a small, calm circle at a trot on your lead rope.
If my ground work is good and I am still having a problem I will use my small lunging circles to help my horse to appreciate standing while being tied up. Before you tie up, lunge your horse for 10 circles both ways or until your horse becomes steady and rhythmical. Then take your horse to where they are to be tied up and let them stand for a short while before giving them a good rub all over. Repeat this lunging exercise when your horse fidgets and pretty soon your horse will lose that desire to be somewhere else and even come to enjoy standing. They will soon realise that standing quietly is much better than the alternative of having to work hard.
As an extra note, take note of the yard’s routine to make sure you are not making things harder for yourself. For example, are you tying your horse up when other horses are leaving the stable block or being fed? Do you always turn the horse out into a field after they have been tied up? Are you using equipment when grooming that makes them nervous and uncomfortable (such as a hard brush on a soft skinned horse)? There could be some small changes you can make to help your horse stand still when tied.