A path gives reps a visual representation of the stages required for working through a sales process in Salesforce Lightning. The Path component is used on the opportunity, lead, campaign, contract, contact, order, and custom object record detail pages in Lightning Experience. Salesforce Path is a visualization tool, used on objects, to help guide users along a Path to a final destination.
Limitations:
Salesforce Path is only available in Salesforce Lightning. We can use only 5 key fields and a Guidance for Success for each section under the Path stages.

Step-1: From Salesforce Setup, enters Path in the Quick Find box, then selects Path Settings and click the enable button.

Step-2: Click new path Button.

Step-3: Then enter the Path name and choose the object, Record Type and Picklist. Finally click Next.

Step-4: This step we have to choose the field for stage by stage to display in key fields area. Now we have select the field for all the stage. then click Next.

Step-5: Now we are going to activate our path. Click to enable our path like below and click finish to complete.

Step-6: Now We are going to see the “How add the path in Lightning page”. Open any one opportunity record, then click the gear icon and choose the edit page.

Step-7: Drag the path from left side to page. and click Save.

Result: Finally we got a path in opportunity record page.

Click here to view more Salesforce blog post.