There's a couple of things you can do to put your Wordle on your blog.
1. You can save your Wordle to the public gallery (there is a button to do this under your Wordle picture). This will produce a code under your wordle that you can copy and paste into your blog - switch the writing mode of your post to HTML (button on the top left) before pasting in the code.
Using this method is not the best as your Wordle will be too small to read. Please use the method outlined below.
2. You could take a "screen shot" or "screen capture". Here's a link to a web site that gives instructions for creating screen shots on various kinds of computers: take-a-screenshot.org.
To make your Wordle larger on screen, you can use the "Open in Window" that appears at the bottom of the Wordle image. You can resize the pop-up window as you like.
Once you've created your image, edited it as you like, and saved it in an appropriate format, you must upload that image to your blog. You can do this by clicking on the picture icon in the menu on the blog post page.
Hopefully this makes sense. Check out other people's blog posts to see what they've done :)