You will first get a screen that shows the persons in the export dataset and a list of options of items to include: private facts, media, etc. I presume you want a "full" split and will select "all" in each case. You can also select a format of Gedcom 5.5 or prior versions of FTM.
You can also click on the Select button to see a list of persons with a count at the bottom. The lingo at that screen suggests you can add and subtract people to that dataset. I've never tried that to see if it works.
FTM automatically gives a name to the file of the old name plus a date - you may wish to change that.
If you want to use this directory to place the file and the related media folder, click ok - otherwise create a new folder or navigate to another folder and click ok.
BTW, this file will be a single *.ftmb (backup) file - which includes media. You will want to RESTORE this file (ie not OPEN). FTM will then create the FTM Media folder and open a *.ftm file.