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 display units on a LogTag model showing temperature on a built in display, you will need to reconfigure the unit using LogTag Analyzer; click on the Advanced Options button in the LogTag Configure window and select the desired temperature units in the Temperature display unit drop down box.