The first time is quite tough. Be sure you have good lighting, and keep your watch face down on a soft cloth.
With a bergeon 1.4 screwdriver, unscrew the four screws MOST, not all the way out.
Do this over a shoe box lid, so if you drop a screw, they won't get far.
then pull the loops out, they'll seperate, and pull them out of the strap.
The 1st time I did it it was at a watchmaker, who tutored me.
It was not simple. Remember the screws have loctite on them.
Try not to scratch the back. Make sure the driver bit is seated well in the groove before you try to turn.
DOn't have the bergeon driver?
A cheaper one ala home depot or sears won't work- I tried.
I bought mine @ 65 w 47th street.
DRS suply 212 819-0237.