Insert time signature:
If one or more bars in a song must be in a different time signature, place the play marker at the beginning of this area and open the „Insert Empty Bars...“ dialog via the „Edit“ menu.
Here you define the time signature and how many bars should be in the new time signature.
Time signature change:
If a time signature change has to be made to an existing song, call the "Change Time Sgnature.." function under the "Edit" menu.
As soon as you have defined the new time signature and the range to be converted, MIDI-Connections Score/Light/Free gives you the information whether a conversion is possible in this range.
A range can only be converted if it can be shared with the new time signature without "commas".