How do I draw a regression line on a scatter plot?

Thank you

There is both a Linear Regression Line indicator and a Linear Regression Line drawing tool which can be added to a chart.

Adding and Moving Indicators
Using Drawing Tools in TC2000

A price chart is a type of scatter plot with time on the x axis and price on the y axis, but if this is not the type of scatter plot of interest, we will need additional clarification from you as to your actual intent.