If you simply wish to change the unit used to display reports and graphs in LogTag Analyzer, select Edit – Options – General Settings and use the drop down list next to Show temperatures in to select the desired temperature unit.
If, on the other hand, you wish to change the temperature units on a LogTag model showing temperature on a built in display, or on the PDF reports produced by the logger, you will need to reconfigure the unit using LogTag Analyzer. Note that the setting is not in the same place for all loggers.