So now you know how to create your first label; if you don't yet, you can read the ins and outs right here. Now, let's see how you can set a label and filter your Conversations using them.
Setting a label
To set a label simply choose the Conversation(s) you want to add your label to by checking the box next to the corresponding Conversation(s).
Once selected, click on the pink 'set labels' button at bottom of the screen. A pop-up screen will appear in which you can choose your created labels and apply them to the Conversation. You can add multiple labels to one Conversation or add the same label to multiple Conversations.
Please note: when selecting multiple labels, only the labels that are connected to all selections will appear in the Set Labels pop-up. This means that all selected Conversations will be overwritten with the current selected labels in the pop-up.
Filtering by labels
If you want to filter your conversations according to labels, just click on Labels (at the top left of the screen, next to the filter) and select the label(s) you are interested in and voila; in your Conversation list you will see all the conversations with the selected label(s).
The Filter tab on the other hand allows you to filter your Conversations according to status or ownership. You can filter using both Labels and Filter at the same time.