I didn't get mentioned! (Cries in a corner)
Jokes aside, all watches have lugs which are the end pointy bits the strap/bracelet/band go between. For your Constellation (and for most watches) you have a springbar that goes in between these drilled holes in the lugs. To remove the springbar, you can start with a tool like this:
One side has a prong that 'fits' into the end of the springbar. The other end is for pushing springbars out if your watch has a hole on the other side of the lug:
To take the springbar out, you gently put the prong side of the tool into the curved slot of the springbar and push down. Do this slowly on a protected surface area. Release the springbar gently so that it drops down onto your work surface. Otherwise it will fly away and you'll spend quite some time looking for it...
Put the springbar into your band. There should be a loop at one end of both pieces of the band. Insert the bar through here. Most of the time the springbar should fit snugly through; if it doesn't, it may be too big or the strap loop is too small. If this is the case, you will need to find slimmer springbars or a bigger strap.
Making sure that both ends of the springbar protrude out of the band, first place one end into a hole on one lug. You then want to use the prong side of the tool and push gently down on the springbar. This will squeeze it down so you can fit it and the band. Once you have the pin inside the lug gently move it from side to side until you hear it 'click' into place.
Then all you need to do is put the other side of the band on!
Practice makes perfect with these - however, there are also people who prefer just asking a watchmaker to do it for them. It is an useful skill to learn though!
I will have a look for you once I'm free
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