How to add or delete label in blogger.com/blogspot.com

Step 1:
Log in to blogger.com, in the Manage blogs, click on edit posts.

Step 2:
To add a label, select the post, you want to add the label.

Then in the drop down menu "Labels Actions..", under "Apply label" option click on New label.

Finally enter the name of the new label.

Step 3:
To delete any label, click on "Select All".

Then in the drop down menu "Labels Actions..", under "Remove label" option you will see the list of all labels, click on the one, you want to remove.

P/s: you need to create new post first before you can add a label