Hi,

Go to the reporting services server.

Normally, http://servername/Reports

Then select the particular report or the entire folder which contains the reports.

Select the properties tab on top and then the security tab in left.
Then click New Role Assignment.

In the text box provided type the username which you got in the error message:

"The permissions granted to user 'TO\username$' are insufficient for performing this operation. (rsAccessDenied)"

Then tick the Browser check box.
Click OK.

That's it.
Thank you.