To make blog posts while browsing other sites and from outside of your Squarespace account, you can use the Quickpost Bookmarklet. This can be installed in the address bar of your browser.
Step 1 - Enter the Content Manager
Click the icon in the Site Manager area to access the Content Manager.
Step 2 - Access Blog Page Settings
On your Blog Page, click the Blog Settings button in the upper right corner.
Note: Each bookmarklet is specific to its parent blog. To post using this feature on different blog pages, you'll need to drag a separate bookmarklet for each blog into your bookmarks menu or browser bar.
Step 3 - Adding the Quickpost Bookmarklet
The Quickpost Bookmarklet is located at the bottom of the Settings menu. To install, drag and drop the Squarespace + button to your browser's address bar, bookmarks bar or menu.
You can then save this URL to the Bookmarks bar of your browser for future use.
Step 4 - Using the Quickpost Bookmarklet
Click the Quickpost Bookmarklet in your Bookmarks bar or list. You can then enter in the content of your post and click Save to publish to your Blog Page.
Note: This Quickpost bookmarklet link contains an encrypted version of your password. Anyone with access to this link can edit your website.