Example of consume a REST API using IONIC 3 article: https://imasters.com.br/apis-microsservicos/ionic-3-consumindo-api-da-marvel
Run the command below to install the dependencies
$ npm install
Then, to run it in a Browser
$ ionic serve
Or to run it in a Device
Android
$ ionic cordova platform add android
$ ionic cordova run android
iOS
$ ionic cordova platform add ios
$ ionic cordova run ios