Doing redirects one at a time can get really tedious.
Optimise Web's Mass 301 redirects give you the ability to update URLs using a CSV file.
First we must create a CSV file.
Using a spreadsheet program, create a new spreadsheet.
The format for redirects, using Optimise's Legacy CSV, is as follows:
old website;new website
with a semi-colon separating the two values. Note that the semi-colon is NOT a delimiter.
Follow this format for the rest of the redirects.
Finally, save the file as a CSV, following Magento's import constraints.
In the Magento Admin, navigate to Optimise Web > Mass 301 redirects
Then, expand the Legacy - Upload / Download CSV File tab.
Browse for the file on your computer, and when finished, click "Save Config". That should be it!
Please Note: Uploading a new file will overwrite the previous file.