how do I find error log to see what is causing the error
The links in the comments are helpful, but don't actually give the correct answer for the log in question.

There's two ways to see the logs for your error:


Check the ConfigAndLog directory.  You can find it here: Where are the &quot;ConfigAndLog&quot; and &quot;templates_c&quot; directories?
You can also see the error on-screen:  Go to Administer menu » System Settings » Debugging and Error Handling, and select both "Enable Debugging" and "Display Backtrace".  Then repeat whatever issue led to the error!  Make sure to turn this off when you're done - leaving it turned on can leak information to a potential hacker, which is why they're not on by default.