1. Click Settings (while still in Edit Layout of Lead/Contact)
Figure: 7577
2. Move the required fields from Avaliable Fields to Selected Fields
Figure: 7678
3. Expand the Buttons Section by clicking on (+) at bottom right corner. Uncheck New check box and move the Custom buttons from Avaliable Buttons section to Selected Buttons section as shown below.
Figure: 7779
4. Click ok.