I installed necessray packages
npm i react-bootstrap-validation", "npm install react-bootstrap
and updated typings
npm update typings
but still getting this error;
How can I tell tyscript I already have that module?
npm update typings you updated a tool, which is used to install typescript definitions. But you didn't install actual type definitions for react.
Actually you don't even need typings, because MS provided their own types publisher. Use this page to search for any type definitions. What you need to do is to run
npm install --save @types/react-bootstrap. This effectively installs typescript definitions for react-bootrstrap.
I really recommend you to take some basic course online around react+typescript (udemy or pluralsight), because these concepts might be very very complicated when start learning from ground without much experience in the field.