I have a requirement to upload data a from CSV file into custom table in Kentico, I have created a custom table but don't know how to upload CSV and process it, I have also created a web part which I can use to upload CSV and Insert data into custom table but that web part is available on front end web page. I want user to login to Kentico backend first and then access a module and upload CSV file.
How can I build a module with a web part to upload a CSV file?
Kentico has quite well documented process of Custom modules creation:
https://docs.kentico.com/k11/custom-development/creating-custom-modules
What you are looking for is a module with custom UI:
In here you are actually creating an ASPX template that will have any controls you need. You can add an ASP button and reuse code from your web part, or add whole web part to the template. If properly configured, module will run within administration and use template of your choosing along with appropriate code.