Suggest you go to the excellent BX DIY website - the fuses summary is here:
http://www.tramontana.co.hu/citroen/electric/fuses.php
As your car is a series II BX use the extreme right-hand column.
Fuses are numbered left to right 1 to 14, though you will only find fuse 14 in use on an ABS-equipped car. Some Haynes sections are available through
www.citroenz.com (though the Haynes BOL isn't brilliant on things electric for the BX).
If the car came with the A5-sized owner's guide, then there's a fuse summary there too.
Back on two wheels and pedal power for the moment.