How to cast on is the first step, an important step in getting the yarn onto your needles. The cast on can be varied depending on the use of the fabric being made and the desired effect trying to be achieved. For instance, socks need to be super stretchy and stay up, scarf can have a straight edge to keep it square. Keep this project simple with a simple cast on.
Gather your supplies:
Yarn
Knitting Needles 
Scissors, Yarn Sewing Needle (to weave in ends) and both
used later into the project.
Yarn and Needles are related to each other.  Check your yarn band for recommendations on
needles size. If using a pattern, the pattern will recommend a type of yarn,
yarn weight and the appropriate knitting needles to use.  
If you don’t know if knitting for you yet since you haven’t tried
it, use any yarn and needles that closely match the recommended yarn
weight.  There are arguments in relation
to the type of needles to use. This isn’t the time to listen to this
discussion, use whatever you have available at present.  
What is the purpose of this piece? Just practice the art of
being present and the art of knitting. 
There doesn’t have to be any other reason.  Just practice your cast on and the subsequent
stitches. After you get the hang of knitting, decide what is going to come of
your first piece.
First piece of knitting. 
What to do with it?  Frog it,
meaning Rip it apart and reuse the yarn for a later project. Keep it as an
example of your first attempt, realise later down the track how far you have come.  Donate a block to make blankets in winter. Or
perhaps, still enjoying the process and keep knitting until you have realised a
scarf has developed out of your new found talent.
The links below are a great place to start your knitting
journey to casting on your first project, or hopefully as a reminder how to
start your next project.
How to CAST ON Knitting for Total Beginners by Sheep & Stitch
Long Tail Cast On (aka Sling shot or Continental method)//
Technique Tuesday by Rozanne Richardson
How to Knit a STRETCHY CAST ON (aka. German Twist Cast On)
by Sheep & Stitch
Everything About Long Tail Cast On LTCO by Knitting with Suzanne
Bryan
German Twisted Cast On and how to seamlessly join it for
working in the round by purLZknitting
Knitted Cast On for Beginners by Snufflebean Yarn
Knitted Cast On by Stephen West
How to Cast On - The THUMB METHOD - Beginner's KNITTING by
Flock & Fern
Master These 6 Essential Cast On Methods! by B.Hooked
Knitting
Once Cast On is complete, go to How to Start Knitting
 
