Depending on the job and the stubbornness of the material being removed, a wall scraper should be held by the handle using one or two hands.
The angled blade on some scrapers means that it is most effective to pull against the material you are trying to separate from the wall.
On this particular scraper, the black wheel just above the blade allows the user to adjust the angle of the head (and blade), and adapt the scraper for different jobs.
Sometimes, particularly in the case of stubborn wallpaper, it is best to scrape in a pushing action, to get underneath the wallpaper.
Make sure you keep an eye on the sharpness of the blade, and change it once it gets dull (See How to replace a scraper blade)