Select a lead (i.e. expanding the lead detail by having selected the white cross in the black circle to the left of the lead)
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The lead detail will now display:
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Select Add tags
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In the Choose tags modal which loads, select a tag
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​N.B. For how to create tags view the article Creating Tags
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Once you select the tag it will be removed from the modal
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Select close on the modal screen and the tag will now display assigned to the lead
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