Add instruction to enable the Allow unsigned toggle

[deepikas20]

Describe your changes

Adding guidance to enable 'Allow unsigned apps' toggle before installing an app.

Checklist before requesting a review

• [ ] I have performed a self-review of my own code
• [ ] I have verified that the code builds perfectly fine on my local system
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have commented my code, particularly in hard-to-understand areas
• [x] I have verified that my code follows the style already available in the repository
• [x] I have made corresponding changes to the documentation