Using labels

Labels allow you to easy organize messages into categories. It does not matter in what folder is the email with associated label located.

Create label
Click in the left menu to the Labels. Then use the icon [+] from the submenu. Enter the name and choose a color.
You can also create a label using the icon  stitky located in the toolbar while reading a message. Use the item Create a new label from the pull down menu.

Assign label
Select the messages in the messages' list and click in the toolbar on icon Labels. Then select desired label from the list. The label will be assigned to the messages.
You can assign the label to the single message similar way while reading it.

Remove label from the message
Display the message for which you want to remove the label.
In the message header click on the cross before label's name.
For bulk removal simply delete the label.

Display messages 
Choose the item Labels in the left menu and click on desired label in order to display all message which have assigned that label

Modify or delete label
In the submenu Labels hover the mouse over the desired label. The action menu appears.
Change name or delete label.