I'm not sure why they told you to CO 4 and then increase to 8
and then join the work in round... but whatever. Maybe the
writer figured 4 stitches was too few to work in the round
without things being awkward? There are several methods of small
diameter circular knitting demonstrated here . Of all of them,
my go-to method is Magic Loop (the video demonstration is
excellent and much more effective than any textual explanation),
and I've started it with as few as 4 stitches (though 8 is much
more common). The problem you might run into trying to join in
round this way is that the increases you've already done might
have tightened the existing stitches to a point where it's tough
to get them up the back side of the needle tips. That's common
in top-down hats when you're just starting out and the increases
are close together like that. You might also be able to CO 4,
divide for ML and do the increases with the work already in the
round (though that seems like it'd give you an awfully pointy
... point on top) OR,