For the visor there appears to be about 24 stitches across the front of the hat. (I have taken one stitch from the corner into this calculation to prevent a ‘sharp’ edge. In fact, I might be inclined to take a second stitch from the edge of the ear flap too, but I would be checking that first by seeing what it looks like when I do that. As the instructions are to crochet 30 you will obviously need to add about 6 stitches or 4 if you take the extra stitch. I do think it might be a bit of trial and error to see what looks best. If you crochet (which you obviously do) you will know to have the right side facing you when you pick up so any line of stitches is on the underside. So, initially I would try to pick up about 2 stitches from the corner of straight edge. Obviously, if there are more stitches than I can see along that straight edge then you will not have to increase so many.
The pattern isn’t particularly helpful about the bits worked in blue - it could have told you where to begin - but my take on it is that you join your yarn at the centre of the back and proceed around the whole hat for one row (join with a slip stitch to the beginning if you like to avoid having to sew up a small gap. Then turn and work round until you get to the front edge of the ear flap - then crochet the chain and go back over it and around the front until you get to the same point on the other flap and then crochet the next chain and work back up it and around until you get to the starting position at the back and join with a slip stitch.
Hope this is helpful, but please ask if I haven’t been clear enough.