There are a few different ways to make line graphs in Google Sheets. The easiest way is to use the built-in line graph function.

To create a line graph using the built-in function, first select the data that you want to graph. Then, under the "Insert" tab, select "Chart...". A pop-up window will appear with a variety of chart types to choose from. Select the "Line" option, and then click on the "Create" button.

Google Sheets will automatically create a line graph based on the data that you selected. You can customize the graph by changing the title, the X and Y axes, and the colors. You can also add labels and a legend.

If you want more control over the line graph, you can use the "Plotly" add-on. The Plotly add-on gives you more options for customizing your graph, including the ability to add interactive elements like tooltips and buttons.

To use the Plotly add-on, first install it by clicking on the "Add-ons" tab and then selecting "Get add-ons". In the "Search add-ons" box, type "Plotly" and then click on the "Install" button.

Once the Plotly add-on is installed, select the data that you want to graph. Under the "Insert" tab, select "Chart...". A pop-up window will appear with a variety of chart types to choose from. Select the "Line" option, and then click on the "Create with Plotly" button.

The Plotly window will open, and you will be able to customize the graph. You can add interactive elements like tooltips and buttons, and you can also export the graph to a PDF or a PNG file.