If you're looking to Download Cacti Viewer on your Chromebook laptop Then read the following guideline.

This is a third-party application for the monitoring software Cacti.  You can download and install the Cacti software to your server for free from the website cacti.net. The minimum tested supported version is 1.2.18. For login credentials, use the credentials directly from the Cacti server; no additional registration is required.  This application serves only as a utility for network administrators who want to have an overview of graphs at hand. This app primarily serves as a widget and an assistant for simplified navigation and easier access to graphs.  - You can create multiple widgets to monitor important graphs. - Easy list up/down devices - Easy access to graphs