Elastic rib puzzlement in Argentina!

hola!

I found a pattern for a beautiful sweater, so i bought all of the amazing and delicious yarn and brought it with me to argentina (where i am currently studying…) haha… then i managed to lose the pattern… long story short, i was able to get it back and i sat down to start the sweater tonight… and! it starts with an elastic rib stitch… this is what i need help with! I don’t know how to do an elastic rib! this probably sounds like a simple question, but i couldn’t find instructions online… nor in my pattern… anyway! any help would be largely appreciated! Thanks soooo much.

I found this:

Elastic rib
With a different coloured yarn cast on half the stitches plus 2 for ends. With the yarn of the work, work as follows:
Row 1 - * k 1., yo.* Repeat from * to *.
Row 2 - k1 end st. *kl into yo., slip purled st. *. Repeat from * to * k 1 end st.
Row 3 - k1 end st. * k1 ., slip purled st. *. Repeat from * to * k1 end stitch
Repeat Row 3 for rib height required.