We have a 2012 QuickBooks local server that we would like to link with this account, we are being asked to a validation code. What do we require to complete this??

Firstly, do you mean that you are installing QB Desktop 2012? Which country version do you have? You have to contact Support to generate the validation code.

Secondly, what do you mean that you want to link QB Desktop to "this" account? Do you want to migrate your data to QB Online or else? Where is your company located?