1. Log in to Google AdSense with your AdSense credentials. Click the 'My Ads' tab. Click 'Get code' under the ad unit you want to use, or click 'New add unit' to make a new one. Follow the prompts to create the ad. Select and copy the ad code.
2. Sign in to your WordPress blog. Click 'Appearance' on the left. Click 'Widgets.'
3. Look to the right to see the available sidebars. Click the arrow symbol on the sidebar you want to insert the AdSense ad in. This will display the sidebar contents.
4. Hover the mouse over the 'Text' widget in the 'Widgets' section. The mouse cursor will change into four arrows that resemble a cross. Click the widget and drag it to the open sidebar. When a dotted rectangle appears, drop the widget by releasing the mouse button.
5. Click the arrow on the 'Text' widget to open it. Right-click on the blank text box and click 'Paste.'
6. Click 'Save,' and then click 'Close.'
7. Wait for a few minutes. It may take a little while for the AdSense ads to appear. Type your blog's address in the browser's location bar. You should see the AdSense ad unit on the sidebar.