Your user manual should explain how in detail with pictures. It is sometimes hard to get the bulb out without breaking it. But try this -
With machine unplugged/power off lay machine on it's back. Locate the light bulb. You probably have a little rubber device in your accessory case that has a suction cup on each end. One end will say In and the other will say Out. Use the suction cup to grab the bulb and pull straight out. Use the other end to install the new bulb in the machine.
If you need a manual - Try this link for free manual for the Viking Rose machine -
There are 2 models called 'Rose'. The original Rose is the manual above. The newer Rose is called the Eden Rose. You can find most user manuals for Viking machines on their website. Here's how:
Go to bottom of page on righthand side and click on 'Machine Updates'.
If your machine is not listed click on 'All Machines"
Scroll down until you find your machine and click on the name of your machine.
The link should take you to a page with a picture of your machine and a link to Download the manual which is a PDF file.