Let's say that, following the instructions on the bookmarklet page, you have copied the "Link to this sentence - A" bookmarklet to your bookmark bar, and now you're working from a list of sentences that have not been translated from language A to language B. You see that two sentences on the page, sentence 1 and sentence 2, have the same translation in language B. (This happens frequently, for instance, when translating from a language whose verb forms change according to the gender of the subject into a language whose verb forms do not.) You can use a procedure like this:
(1) Translate sentence 1 into language B without leaving the page.
(2) Right-click on the green bent arrow next to your new translation and copy the URL ("Copy Link Location" in Mozilla Firefox, "Copy shortcut" in Internet Explorer, "Copy link address" in Google Chrome).
(3) Right-click on the round blue "i" icon next to sentence 2 and select "Open in new tab" or "Open in new window".
(4) In that new tab or window, click on the "Link to this sentence" bookmarklet. When prompted for a URL or ID, paste in the one you copied in step 2 and hit Enter.
(5) If all went well, you will see the link you wanted to create and a message saying that the sentences have been successfully linked. (Otherwise, you will see an error message.)