Do this by going up to the Omnibox (where the website URL is across the top) and right-clicking in it. Then choose "Edit Search Engines".
Under your default search engine settings, you'll see an "Other search engines" section. Look to the right to find the "Add" button.
Google Drive: https://drive.google.com/drive/search?q=%s
Chrome Web Store: https://chrome.google.com/webstore/search/%s
When you are done with one entry, click "Add". Then you can repeat the process to add more.
Now, no matter what website I'm currently on, I can go to the Omnibox and type in dr and hit spacebar or tab. Then it will be ready for me to search Google Drive. I can do the same thing by typing cws and then hitting spacebar or tab. Now I can type in what I want to search for in the Chrome Web Store. It's a beautiful, time-saving thing!
You can do this for most any website - Amazon, YouTube, Bible Gateway, etc. Just repeat the process we did above. To get the correct URL, you'll need to search for something on the desired website and copy the URL of the search results. Then when you paste it into the new search engine entry, replace the word or phrase that you searched for (and anything after it) with %s.