It´s not too difficult. You just need to fill out an application that fulfills all the requirements, and if you´re chosen, you´ll be notified in the following months.
One of the most important requirement is that you need to have is good writing skills, including spelling, punctuation and syntax.
On your part, you need to be able to manage your time, so as to write the assignments without delay.
two to four hours a day will be sufficient time to write the articles assigned. it all depends on you.