The export/import is done under LOG and is in the top right of the LOG screen.
It looks like Howard suggested that, first you export your current log and then proceed to import a fresh log.
Take a look there and see if that is more clear, and fyi, import is at the bottom of that drop down, it isn't visible unless you go lower in the selection window.
73 - Mark - K8MHW
'A RigPi Enthusiast!' - I am not otherwise affiliated with MFJ or RigPi