Open the SharePoint site in SP Designer, Click on workflows which is available in the left hand side.
Click on the workflow that you want to export as per the below screen shot.
Save the workflow as per the below.
Workflow is saved in your system in VMI format.
How to Import SP Workflow
Now if you want to import the same workflow in any other site.
Follow the steps as per the below.
1)Add the .ZIP extension for the imported workflow and click on YES as per the below.
2)Open the Zip folder and delete the workflow.xoml.wfconfig.xml as highlighted in the below.
3)Right click on the workflow and remove the .ZIP
4)Again we can able to see the workflow in .VMI Extension.
5)Open the Site in SPDesigner that you want to Import the workflow into that particular site.
6)Click on “Import from Viso” as per the below screen shot.
7)Select the workflow path and click on Next.
8)Select the list that you want to associate the workflow and click on Finish.
9)Save the Workflow and update the changes in your workflow then save and publish.