npm install ionicons

add the code below to "assets" in the angular.json file.

{
   "glob": "**/*",
   "input": "./node_modules/ionicons/dist/ionicons/",
   "output": "./ionicons/"
}

add the import below to "scripts" in the angular.json file.

"./node_modules/ionicons/dist/ionicons.js"

We’ve started by importing CUSTOM_ELEMENTS_SCHEMA from @angular/core and added it to the application’s @NgModuledeclaration in the schemas property.

You can now use ionicons as you would expect: <ion-icon name="heart"></ion-icon>