Please put the staple in on a 45 degree angle at the top left corner of the document.
ーPlease put the staple in on a 45 degree angle at the top left corner of the document.
「書類の左上に45度の角度でホチキスを留めてください」
to put the staple in で「ホチキスで留める」
on a 45 degree angle で「45度の角度で」
at the top left corner of ...で「…の左上角に」
document で「書類」
ご参考まで!