Hi and welcome to Knitting Help!
You can find many of these abbreviations on the Glossary tab at the top of this page, some with a video to demonstrate the technique.
Decrease Row 1 (RS): K1, [k2tog, k8 (10) sts, ssk, pm] 7 times, k1—72 (86) sts remain. Knit 5 rows.
k2tog is a knit 2 together decrease that gives you a right leaning slant, ssk is a decrease that gives a left leaning slant. pm means place marker. The stitches in the brackets are repeated 7 times and the numbers at the end give the number of stitches you'll have at the end of the row for the small (large) size.
Decrease Row 2 (RS): Change to St st. Decrease 14 sts this row, then every 4 rows 3 (4) times, as follows: K1, [k2tog, knit to 2 sts before marker, ssk, sm] 7 times, k1—16 sts remain. Work even for 3 rows, removing markers.
St st is stockinette stitch, a pattern of alternating knit one row, purl one row. Work even means to continue without increases or dcreases.
Decrease Row 4 (RS): [K3tog] 3 times—3 sts remain. BO all sts.
k3tog is knit 3 together, the same idea as k2tog but with 3 stitches instead of 2.
That should get you started on the bib section. See how it goes on that part and then we can help with the rest. Because of copyright problems, would you delete the rest of the pattern please, so that the entire pattern isn't posted here?