Dell POWEREDGE M1000E - Manual (Page 464)

464 Configuring a Captive Portal
4 Browse to the directory where the image to be downloaded is located and
select the image.
5 Click Apply to download the selected file to the switch.
6 To customize the Authentication Page, which is the page that a user sees
upon attempting to connect to the network, click the Authentication Page
link.
Figure 17-9. Captive Portal Authentication Page