well its quite simple.
you don't have to worry about anything, just choose your product and place your order, rest seller will do his job.
Sellers mostly choose China Post to send their products and you will receive the product at your home.
So double check your postal address and make sure everything is correct.
but keep in mind that DHL is way too much expensive, as suggested you can choose this method if you need anything urgently.
china post usually takes 20 to 60 days to deliver the product as there are many factors that affect the delivery timings.
don't order too much expensive products,mobile phones, other electronic as they may be held by customs.
best of luck