Apply for Google AdSense account
According to Google AdSense policy- you must have a very useful site with 6 months old domain. However, in some cases, AdSense approves the account even for new sites and blogs.
Don’t think of AdSense for at least 1 month. Only focus on writing and quality writing.
Write at least 10-12 high quality article in your blog before you apply for AdSense. Once your site become at least 1 month old, you can apply for AdSense.
It takes 2-7 days to get the approval from Google AdSense. In most of the cases, Google will give you approval if you follow as I said.
In a rare case, they may reject your application. You can then write more articles and apply again after 1 month and now there is very good chance they will approve your account.