I have created a custom list named “K2 Workflow Tutorials” in which K2 workflow will be created to update subsite. Please refer to my previous article to create a K2 workflow in SharePoint 2013 Online.

Go to K2 designer, drag and drop Update Subsite step from the Sites Workflow Steps in the ribbon interface.

Select a site collection and then click Next button.

Specify filters for the subsite to update and then click Next button.

Specify values for the subsite to update and then click on Finish button.

Deploy the workflow. Create a new list item in “K2 Workflow Tutorials” list with title field value as “TEST SUBSITE” and description field value as “Test subsite updated using K2 workflow”. After few minutes the workflow will be completed and the subsite which has title field value “TEST SUBSITE” will be updated.