Go to the SharePoint Store from your SharePoint Online site or Microsoft Appsource.
Search for "Virto Gantt Chart" and click "Add" to install the app.
Add the Virto Gantt Chart web part to your SharePoint page.
Configure the data source by linking your SharePoint lists to the Gantt chart.
Adding Tasks: Click on the chart and enter task details.
Modifying Tasks: Use drag-and-drop to adjust durations, dependencies, and completion percentages.
Customization: Customize the chart's appearance and timescale to fit your project needs.
Advanced Features: Manage multiple projects, export charts, and set user permissions.
For more detailed information about product setup and other details, please refer to the Virto Gantt App for SharePoint Online Documentation.