To type in Bishall font, we need to learn about the Nepali characters that the English keyboard's keystroke will raise.
The keyboard layout/character map of Bishall font is more or less similar to other Nepali fonts. If you have used Preeti font previously or any other Nepali font, it wouldn't take long to get used to the new character map. Even if you haven't worked with Nepali font and this is your first time, regular practice will be enough to make yourself familiar with the character map. Practicing on a standard English keyboard is recommended, as it will make working with any hardware easier.
Character Map of Bishall Font: