There are two tabs available here, one for setting up communication with a GPS device and one for setting up replay of previously recorded journeys.
General
Device communication
Communication protocol - Select the data output protocol of your device. In the vast majority of cases this means NMEA
Port - Select which port your device is attached to. Note that if you have a USB receiver, a COM is still created by the USB driver. In windows go to Control Panel/System/Hardware/Device Manager/Ports (COM&LPT) to find out which port your device is using.
Set the speed etc. at which your GPS unit communicates. Make sure that Baud rate, Byte size, Parity and Stop bits match the settings of your COM Port.
Timing
Select how often you want your position to be updated on the map. One second is the lowest time interval (the highest update frequency).
GPS devices usually communicate Greenwich Mean Time (GMT). If you are in a different time zone or in the UK when clocks have changed to British Summer Time (BST) then you can adjust the time displayed and recorded with the Time offset spinner. As an indication, BST is set as 1 hour ahead of GMT.
Replay
Live speed replay - select this option to replay a file at the same speed at which it was recorded.
Accelerate replay - select this option to replay a file at a higher speed than that at which it was recorded. Use the spinner on the right to set the replay acceleration.
Skip time gaps larger than - this is a useful feature which lets you skip parts of the file where the position is stationary. Use the spinner on the right to select what sized gaps to skip.