Step 1:
Create Sharepoint List that contains the data you would like to report against.
Step 2: Once in SSRS:
1. Create a new datasource
a. Name – Name of datasource
b. Type – XML
c. Connection String – Home page of the Sharepoint site where the list exists.
NOTE: After the name of the site remove the “default” and replace it with <</_vti_bin/Lists.asmx>>
http://<server>/<path>/_vti_bin/Lists.asmx
d. Use Windows Authentication