It helps you tell us what you're making and post a link to the pattern when asking questions.
One thing you can do is knit a couple rows flat if you're doing garter or ribbing THEN join. It makes it easier not to twist the stitches if you can see them. Then at the end you can use the tail to seam that small area.
To join you need to divide the stitches on each needle by slipping them purlwise. - that is straight into the stitch as if to purl it not as if to knit - Then with the working yarn on the needle on the right you just hold the two closest needles and start knitting. Here's a couple visuals if it helps.