public class ProcessHandlerShowAccounts
{
    public class AccountParameter
    {
        @InvocableVariable(required=true)
        public Id accountId;
        @InvocableVariable(required=true)
        public String name;
    }
    @InvocableMethod(label='handle' description='Send the Accounts variables passed from Process Builder to the webservice')
    public static void handle(AccountParameter [] accountParameters)
    {
    webServiceCallOut(accountParameters[0].accountId,accountParameters[0].name);

    }
    public static void webServiceCallOut(ID n, String a){
        Http http = new Http();
        HttpRequest req = new HttpRequest();
        req.setEndpoint('https://Accounts'
                    +'?sfdcid='+n+'?operation='+a);

        String username = 'nameishi';
        String password ='123';
        Blob headerValue = Blob.valueOf(username + ':' + password);
        String authorizationHeader = 'BASIC ' + EncodingUtil.base64Encode(headerValue);
        req.setHeader('Authorization', authorizationHeader);

        //Create a new Http object to send the request object
        //a response object is generated as a result
        HTTPResponse res = http.send(req);
        System.debug(res.getBody());
    }
}