...
- Select your VM in the overview list.
- Go to the Networking section.
- Select the interface tab of the relevant interface.
- On the interface tab page, click on the interface name link next to the Network interface link label.
- On the network interface page, under Settings (in the left-hand pane), select IP configurations.
- Click on the name of the IP configuration (in the list at the bottom of the page) to which you want to add the public IP address. This will open the IP configuration screen.
On this screen select Enabled Associate for the Public IP address. This will allow you to select the new public IP address.
Then click on Save (at the top of the section) to save the changes.
Please note: do not forget to add an appropriate Network Security Group to protect the interface.
...