[1] Add persons who borrow your DVDs/BDs to your user database: "Tools" --> "Edit Users" (don't forget to check "Borrows DVDs").
[2] Optionally change the default loan period in the options ("Tools" --> "Options").
[3] Select a profile, click the "Loan to" icon in the toolbar (resp. from the menu "DVD") and choose a user. Choose "Loan to custom" to use another loan period than the one defined in the options.
[4] You can see a list of all loaned DVDs on the welcome page.