Answer to your query does not need a detailed explanation, but lets put it in simple words for clarity.
1. If you do not have a Google Adsense account.
In this case, as you mentioned that you have a blog and want a new Adsense account for earning revenue from Google ads displayed on your blog.
- First of all, you need to post good quality content on your blog and they can be of any niche category/specific category, for example, cooking tips, stitching tips, product review, technical analysis, etc.
- You must have at least 20 to 30 posts of the category chosen by you and also do its promotion to get some traffic to your blog. User must visit your blog and also stay on the same for some time/read your articles/posts.
- After this you must apply for Adsense program from your account only. You do not any host or client service kind of thing.
For this you must log in to your blogger account and and see on the left sidebar, where a earning tab will be mentioned. You must click on the same and apply for monetization of your blog.
Your application will be submitted to Google ans it will review your blog and a message will be displayed that it will take 2 weeks to verify and assess your blog for monetization.
You must wait until 2 to 3 weeks before Google reverts with a reply for approval of your Adsense account. You must login regularly and keep posting new articles/posts and share them regularly and at the same time check the status of your approval of Adsense account.
Try not to visit your own posts/blog unnecessarily to increase the number of visits, as Google can verify the same through your IP and device ID.
If your blog has good and unique visits then your blog will surely get approved and an Adsense account number allotted to your blog which can be used on that blog only.
Keep your posts original and do some keywords research before posting content so as to get good ranking and search results.
2. If you already have an approved Adsense account.
If you already have an approved Adsense account then there is no need for much effort. You just need to login to your blogger account and on left sidebar you will see "Earnings" tab.
You will have to click on the same and click on display ads on your blog button and save the settings. The ads will automatically start to be displayed on your blog if you have used default theme of blogger.
In case you have chosen some third party theme on your blogger account then you will have to make some changes in your theme layout and insert the Adsense code manually for ads to display on your blog.
To get the Adsesne code you will have to login to your Adsense account using your gmail id from which the blog was created here: https://www.google.com/adsense
Once you will login you need to click on "Ads" on the left sidebar and the click on "Get Code". I have attached an image for your reference.
Hope the explanation did not become too technical, the more you use the blogger and adsense account, the more easier it will become and anyways help is always available to those who seek for it.
Live before you leave.