This tutorial introduces the Wizard of Approximation.
Select data series on left panel [Points].
Select menu item
The 'Approximation line' Wizard appears.
On step 3 select Family 'Exponential' and Function 'ExpGrowth3'.
The form of equation is 't = a + b*exp(x/c)'.
On step 4 click
New graph appears. See how curve fit conforms your data.
On step 5 select line color and click
Close the dialog and select menu item