Tags are useful for delineating subjects, organization, content highlights, and many other uses. To maximize your tags' usefulness, you should check the tag list before creating a new tag to make sure you don't already have that tag (with a different capitalization or part of speech, for instance). You may also want to consult What is metadata and how do I use it? for further information.
To add tags to an item, click to the tags tab of the metadata pane. Select Add Tag, then type your new tag name. Press Enter to save your tag. That tag now appears in the tag list in the sidebar, as well as in the tags tab of the metadata pane.
You can also add a new tag to a group of items. Ctrl/Command+click or Shift+click to select the items, and then click on the tags tab of the metadata pane. Select Add Tag, then type your new tag name. Press Enter to save your tag. The tag is now applied to all the items you have selected.
To access all of your items tagged with a particular tag, click on the tag name in the sidebar.
You have two options for adding a tag that already exists. You can either (1) drag and drop your item onto the tag in the sidebar; or (2) right-click on the item, then move to Tags and select the tag you wish to apply. You can also add tags in bulk, by selecting multiple items and then either dragging and dropping or selecting a tag from the right-click menu.
In the tags tab of the metadata pane, you can also click Add Tag to Item, and then starting typing a tag, and you will see suggestions of existing tags to autocomplete.
You have two options for renaming a tag.
In the tag list in the left menu, right-click on the tag, and select Rename tag. Enter the new tag name and hit return. The tag will be renamed in all the items to which it has been applied.
In the Tags tab of the metadata pane, right-click on the tag, and select Rename tag. Enter the new tag name and hit return. The tag will be renamed in the tags list in the left menu and in all the items to which it has been applied.
In the tags tab of the metadata pane, click on a tag to select it and then press Backspace to remove a tag from an item.
In the sidebar, right-click on a tag and select Delete tag.
Once you have created a tag, you can assign it a color. In the tag list in the sidebar, right-click on the tag name and navigate to Change Color. If you assign a color to a tag, items with that tag will receive a small colored circle in grid view so that you can easily see which items have colored tags.
You can assign all of your new tags a default color. Right-click on the word Tags in the tags list in project view and select Default Tag Color. Once you've selected a default tag color, all new tags will have that color automatically (though you can change the color using the same menu).
To view tagged items, click on the tag name in the sidebar. The items with that tag will appear in the item table. Note that if you have a list selected, only items within that list will appear in the tagged-items results.