I am sorry I can't help you with the pattern but when you are knitting on circular needles, I find it easier for me to keep track of the beginning of my rows by placing some type of marker before the first stitch of the row ( i.e small piece of contrasting yarn, saftey pin, smal plastic ring etc.)
When it says to join , you are continuing to knit in the next stitch ( you may want to pull yarn a little extra tight between the last stitch of the last row you worked and the first stitch of the next row you are going to work ) so you don't have a hole in your finished work.
Also, when knitting on circular needles , when you are knitting something like a hat or skirt, after you have chained the requires sts. be extra careful that your yarn does not twist when you are joining or you will end up like me having to take it all down and start over again.
I hope this helps sorry if my explaination is confusing. I am sure someone will come and explain it better. Happy knitting.