Edit in JSFiddle

//the API must be loaded for the method to be used
GameAPI.loadAPI(function(apiInstance) {
    // Gets the object that contains the data regarding the game link related to the 'app_store' label set in the game configuration from Spil Games backend
    var linkLabel = 'app_store';
    var app_store_link = apiInstance.Branding.getLink(linkLabel);
    if (app_store_link.linkName === linkLabel) {
        // if you have the image set from Spil Games 
        // backend you can use  app_store_link.image 
        // in order to retrieve its URL
        // use app_store_link.action as the handler for 
        // the interaction with the game element