When you do a yo before a purl, then yes, you have to bring the yarn up over the needle and back to the front again.
After a purl depends on what comes next. If it's another purl, then do it as above; if it's before a knit, then you can work it from the front.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry