Marking stiches

Hello all,
I have been knitting for about a month now and I’ve decided it’s time for me to attempt to knit a sweater. So I’m working on what looks to be an easy pattern for a baby sweater (I’m about to have a niece). I’ve been teaching myself to knit mostly by book and online, but I’ve got to a place where I’m stuck. The pattern wants me to “place sleeve markers” then continue for a while and “place shoulder markers”. What does that mean?

They’re little rings you put on your needles between stitches and slide from needle to needle as you knit to keep your place (or sometimes put on actual finished stitches for future reference or to mark length).

You can buy solid plastic rings. Plastic rings that open and close. Use a paper clip, a safety pin, a bread tie, a piece of yarn and a whole bunch of other things.

Here’s the basic ring type.