Hi @Priya1601 

I will suggest to follow Structured learning. 

• First again complete  ServiceNow Administration Fundamentals  course from Servicenow University
• Practice again all lab task in The given learning instance.
• Practice in your Personal Developer Instance (PDI)
• Complete CSA

• Secondly complete  Certified Application Developer (CAD) Learning Path  course from Servicenow University
• Practice again all lab task in The given learning instance.
• Lots of videos are there Practice it.

AT the end. If you want to take help of AI to create application, 

Use Build agent. In your PDI you will get it.

https://www.youtube.com/watch?v=1_FpBxHV-0k