Make sure you are signed in before searching for an item via Library Search, If the item you need is not included in the results list click 'click here to expand your search' at the top of the results to see items beyond the Derby collection.
If the item you need is now displayed you will see the label/link 'Get it for me from other libraries' which will allow you to request either a physical or digital copy if available. Click on that label/link to open a request form. You can find more information with screen shots on the Inter Library Loans page; scroll down until you see 'How do I submit a request?'
If you are searching on other library databases (ie. not using Library Search) and find resources that are not immediately available you can complete a blank Inter Library Loan request form giving full details of the item you need.