1. Click Settings (while still in Edit Layout of Lead/Contact)
2. Move the required fields from Avaliable Fields to Selected Fields
3. Expand the Buttons Section by clicking on (+) at bottom right corner. Uncheck New check box shown below.
4. Click OK
5. Save Contact/Lead layout
Next Step
Using Sitecore Analytics in Salesforce (Version 3.x)
or
Using Sitecore Analytics in Salesforce Lightning (Version 3.x)