How to Put Stirrups on an English Saddle

[@me_krackers]

this really helped me tysm im a first time loaner and the curren stirrup leathers are to long so i need shorter one I am completely blindsided. No one has ever told me how to tack up ,how to adjust stirrups, how to put on a bridal until when I started loaning. The owner showed me how to tack up briefly so this is really helped me thank you

[@user-sb5fr2xz7f]

I got an extra piece that I think is supposed to go on the back, there are little round circles. Do you know what those are?