the "recommended' method for removing items from backup is to enter time machine and find the item (which may require going back some days if it has since been deleted from your main hard drive), right click on it, and select the "delete from all backups" option. This will go into the TM drive and remove all hard links to the file made at each backup run it was present at, as well as removing it from time machine's search database.
Directly browsing the time machine backup using Finder will find the files, but if you trash them and empty the trash, you're unlikely to see an increase in available disk space since you most likely removed only one of the hard links to the file. With other hard links remaining (from other older backups) the file will continue to hold space on the drive. Such an action may also make it more difficult to locate and remove the file using the time machine interface, since the DB will expect the link to be there but it's not since you have directly deleted it. (you may have to dig back farther in time to find one that's still there to select for removal)
