Customer's have Asset records that relate to their Accounts and their Restocking Addresses (Customer Sites).
When we're performing a Service we want to be able to track exactly what items we're Servicing.
This is important because we'll use this information to understand when an Asset is due to be serviced again, as well as using the Service as an opportunity to check and update the details for the Asset.

Assets also allow us to show Kit Definitions - lists of Items that belong in that Asset, which are useful when determining what you need to Restock and how many of each Item are required.

When an Asset is added to a Service we create a 'Work Order' record for it.
You'll never directly edit with this Work Order, but it's useful to understand what's happening in the background.
The Work Order for an Asset is where we'll put Line Items that track the inventory used during the Service, it's also where we'll track if you've finished Servicing the Asset or if there's still work to be done.

When you first open the 'Assets and Service Orders' tab you'll see the starting layout of the Servicing Module.
On the left-hand side are two lists, the list of Assets that have already been added to the Service and a list of Assets belonging to the Service Account that could be added to the Service.

The 'Add Assets to Service' component shows all Assets that belong to the Service Account, not just the Assets that belong to the Restocking Address (Site) that you're on.

The reason we do this is because sometimes an Account might have an Asset that's tracked against a 'Service Vehicle' or a mobile site, and they might want you to Restock it while you're there.

There's also a very helpful piece of information on this list: the 'Location' field. The Location is where an Asset is physically located inside of a Customer Site, it's going to be the best way to differentiate between two otherwise identical Assets.

Selecting an Asset for a Service is as simple as selecting the 'Add' button to the right of the Asset.
If you've added an Asset that you didn't mean to, don't panic! As long as you haven't already delivered any items for an Asset you can use the 'Remove' button in the 'Selected Assets' list to remove it from the Service.

Sometimes a customer will have an Asset that isn't already recorded in Salesforce. You can quickly add a missing Asset by using the 'New Asset' button available in the 'Add Assets to Service' component.

Detailed instructions on how to do this are available here: Creating an Asset Step 1