1.   You can create a new  Task list or can use the existing task list in your site

2.   Next step is to find out the GUID of the task list that we want to add in the work flow

Find The GUID of the list

There are different ways to find out the GUID of the SharePoint list here I am showing the simplest one.

3.   First go to your SharePoint list  then select List Settings

4.   From the url copy all the things after “?List=”

5.   Change “%7B” to “{” 

6.   Change all “%2D” to “-“

7.   Change “%7D” to “}”

You got the GUID of the Task List

 8.   Open the site with SharePoint Designer select the work flow you created, expand out the “Workflows” folder and the workflow whose Task list is to be changed.

9.   Open the file named yourworkflowname.xoml.wfconfig.xml

10.Replace the Id in the “<Association>” element’s “TaskListID” attribute with the GUID we found out now.

11.Save and you are done