Please don't promote blogs that aren't in the Mumsnet Bloggers Network. Join the network
To use this feature subscribe to Mumsnet Premium - get first access to new features see fewer ads, and support Mumsnet.Start using Mumsnet Premium
Go into the design page for your blog, and you should have an opportunity to rearrange the "gadgets" (little boxes) on your blog's page. There's also the option to "Add a Gadget" in the draft layout of your page.
If you click that, you should have a list of options for what sort of "gadget" you want to put (like a search bar, archive, etc.)
Choose the one that mentions HTML, and you should get a little text box to copy the button link into. Do that, put it somewhere on you blog, and voilà!