Adding another ball of yarn

HI! New to knitting. I am making a rather large scarf with a rib pattern. I am running out of yarn and need to add more from another ball. How do I do this?
Also, how can I make a ball from a skein of yarn? I spent over a week trying to make a ball last time.
Thanks for any info you can offer me.
Happy Knitting!!:knitting:

If you have a pull skein, you don’t need to make a ball. If it’s a long hank/circle of yarn, there’s a video on this page near the bottom The same page also has tips on how to join your yarn. I tie a loose knot with the two ends, knit a few rows, then readjust and tighten the knot.

You can make the two skeins into one with a felted join (for animal fibers) or a Russian join (for all other fibers). Both of these hide the ends and make it so there’s no loose ends to weave in later. You can see how to do them on the tips video page.