Click your blog in the dashboard.
Go to Posts.
Click on a label (clickable orange text next to the blog title). You may also click on on the upper right dropdown list of labels to show the specific label you want to show.
The list will refresh to show you which posts use that label.
Click on the tag icon and choose from the drop down menu the label you want to remove from that post. Take note that if a post DOES NOT HAVE THAT LABEL, it adds the label automatically. All posts selected SHOULD have that label to have them removed.
If successful, a message will prompt of the removal.
EXTREMELY IMPORTANT TIP: If you are decluttering labelsin batch, make sure that before proceeding with the next label, REFRESH that page first. This act makes sure that no blog has been ticked. I almost have thrown my laptop when after removing a label, it adds them to multiple posts afterwards :-(
Another behaviour you should be aware of: once there is no post with that label, that label will be removed from the list.
Side comment: So effin' inconvenient if you ask me.