After enabling Handwrite in your settings, you’ll see a new icon in the bottom right hand corner on the Google homepage and Google search results pages. Tap it to write anywhere on the screen.
Handwrite can only recognize legible characters. Writing with straight block letters will return the best results.
You can search by writing just a few letters at a time. From there, you may see an autocompletion for exactly what you’re looking for - just tap it to search.