To create a lead tag, go to the lead that you would like to assign the tag to.
Click on Add New Tag
Enter in the New Tag name and click on the Add button
Next click on the Select Options area, in order to assign this tag to the lead. Select (check off) the lead tag that you would like to use.
NOTE: You will only need to create the Tag name once. Afterwards you can skip the above steps and just go to the Selection Options step.