Create custom NPM Package. its not work in ionic project

Here I create one NPM custom package for requirements it’s successfully installed on my ionic project. and this is the first time in my experience I have build NPM custom package.
My issue is when I try to import it like import * as CustomNpm from 'CustomNpm'; it gives me an error that “Can’t find module CustomNpm”.

Then how can I import my custom package in ionic(ionic-3) project and any code required in NPM class export?

Thank you in Advance.