Assuming you are referring to the Gantt chart tool called Instagantt:
First, create an account and log in.
Once you're logged in, you'll be taken to your dashboard. To create your first Gantt chart, click on the "Create New Project" button.
Enter a name for your project and click "Create Project."
You will be taken to the Instagantt interface, which is a drag-and-drop Gantt chart tool.
To create a task, click on the "Add Task" button and enter the task name, start date, end date, and duration.
You can also add subtasks, dependencies, and notes to each task.
Once you have added all of your tasks, click on the "Save" button.
Your Gantt chart will be saved and you can share it with others by clicking on the "Share" button.