The NETS agreement is basically an agreement between your bank and Pleo, which, when signed by the signatory ('tegningsberettiget' in Danish) in your company, makes it a lot easier to transfer funds between your bank and Pleo.
You can, once the NETS agreement has been set up, top up the wallet directly from Pleo or set up an automatic transfer. With the latter set up, you can rest assured that your Pleo wallet never runs dry. You can read more on how to set up the automatic transfer here.
Prefer to top up your wallet directly from Pleo using NETS? You can do that as well with just a few clicks. Simply enter the amount you wish to top up with (5,000 DKK is the minimum) and click 'Place top up'. A bank transfer will be initiated right away - and you can see when it's expected to reach your Pleo wallet in the Wallet page.