This short article shows you how to resolve the error “The option for the SharePoint 2013 Workflow platform is not available in sharepoint designer” in SharePoint Designer 2013.
2. Follow this article to install Workflow Manager to SharePoint 2013 https://technet.microsoft.com/en-us/library/jj658588.aspx. Anyway there is one important statement you should take note.
Register-SPWorkflowService -SPSite “http://win-9aarjh8n2qu/sites/SharePointDevelopment/” -WorkflowHostUri “http://win-9aarjh8n2qu:12291” –AllowOAuthHttp
But the article miss an important statement before that.
3. Now you should be able to use SharePoint 2013 Workflow in SharePoint Designer 2013.