What does Place all sts on a holder and break yarn?

It means a stitch holder. There are various kinds. The ones like a big safety pin I think are best.

If you do not have a stitch holder use a safety pin if there are just a few stitches. For more stitches put them on a spare needle any size the same or smaller than those you are using will do. Or you can thread them on a length of spare yarn

A "holder" is a place to store your live stitches so they are temporarily not on the knitting needle.

Here's a link so you can see what a stitch holder looks like: http://www.nobleknits.com/products/Clover-Double-E...

"Break Yarn" just means to cut the yarn. Be sure to leave about a 6" tail. You don't want to cut it too close to the stitches or the stitches will unravel.