If you have a batch that all need the same White Balance there are two quick/simple approaches:
To start with you need them all together in the Film Strip. If they are all in one folder, good, otherwise you can put them in a Quick Collection so if you open the Quick Collection they will all show up in the Film Strip!
Then:
1) A quick way is to use the Auto Sync function: in the Develop module, select all the photos in the set that you want to have the same WB. On the bottom right of the module are two buttons. One is Reset, the other (on the left) will either say Sync... or Auto Sync. To use the Auto Sync, if it is not showing that label, click the little button to the side of that button so that Auto Sync is turned on. Then, again with all the photos in the set selected (your "first" one will show in the main window), go ahead and adjust the WB on that first one. When you do make an adjustment to the first image (and "finish" the adjustment) the adjustment will be automatically applied to the rest of the selected images.
This approach is good for a quick "global" adjustment (or more than one if you wish) for all the photos.
2) The second approach is good if you want more flexibility: click that little button to change the Auto Sync to just Sync. Then you can work on an image alone, and when you have edits that you want to "share" select the others in the batch (ensuring that the "master" is the "active" image). Then if you click the Sync button and options window will pop up. All the various develop setting show up with check boxes. If you only want to apply one setting (such as the WB), then click the Check None button and then click on that one setting check box. Then click Synchronize and the setting will be applied. As you can see, though, you can pick and choose what to apply -- I typically work on one image for various adjustments and when I'm happy with it I'll Sync and maybe apply everything but say a crop that I've done to the one image. It's a good tool to play with.
There are other approaches but those are the ones I use.
One thing that is important, though, when working with the WB and Sync: If you end up with your "master" shot having the "As Shot" setting, then Sync, the other images will keep the "As Shot" setting, in other words they won't be changed! So you want to make sure that you do an actual adjustment or change to a WB preset!