Add Google Adsense to your WordPress website follow these steps.
Step 1: Login to your Adsense account.
Step 2: Adding your website to Google adsense.
Step 3: Click on Add site
3.1: Add URL of the site where you want to display the google ads and Save and Continue.
Step 4: On the next page unique google adsense code will be generated. you will need to copy that google adsense code for wordpress site.
Step 5: Now adding Google adsense code to your site.
Step 6: Paste the Google adsense code in the Index.php file located in the Apperance > Theme file editor > index.php
Step 7: Save Settings and Request review.
Step 8: Show ads in every page of header section you need to install plugin Header and Footer scripts and paste the google adsense code there.
For complete procedure watch the detailed video.