To perform a search on ChemSpider from MassSpecBlocks you need to have an account on ChemSpider and have created an API key on it. Then you can store the API key to MassSpecBlocks on the Settings page.
To obtain the API key you need to go on ChemSpider web. Click on Web APIs in the top header.
Then click on Get Started button.
After that, you see a page with a tutorial, which you need to do to obtain the ChemSpider API key.
