I am trying to correct an issue with a package I am using called Custom Related Lists. The error I am receiving is shown below.

Script-thrown exception
Error is in expression ‘{!generateCode}’ in component in page crl_newcrl: Class.ToolingAPI.submitRestCall: line 476, column 1
Class.ToolingAPI.submitRestCallAndDeserialize: line 418, column 1
Class.ToolingAPI.createSObject: line 79, column 1
Class.CRL_CodeGenerationLib.GenerateClass: line 9, column 1
Class.CRL_NewCRLCtrl.generateCode: line 220, column 1
Caused by
Class.ToolingAPI.submitRestCall: line 473, column 1
Class.ToolingAPI.submitRestCallAndDeserialize: line 418, column 1
Class.ToolingAPI.createSObject: line 79, column 1
Class.CRL_CodeGenerationLib.GenerateClass: line 9, column 1
Class.CRL_NewCRLCtrl.generateCode: line 220, column 1

Someone posted what seems to be a simple solution but I have no experience using Developer Console. Here is what the solution is.

I was able to get this to work by adding a new remote site in sandbox. For others that run into this error, jump into your developer console and identify the endpoint URL that needs to be added as a new remote site and your custom related lists will generate perfectly.

I have no clue how to do what they are describing above. Any help would be appreciated.