To add a page, go to the Carrelet control panel, select the page after which you wish to insert the page, and click Go. Note that if you have not changed the menu entries of the existing pages, you will see two entries with the same page number, the page that used to be where the new page is and the new page itself. The page numbers displayed in Carrelet control pages are the 'real' ones, ie page 4 corresponds to the file index4.html. You can check the 'real' page number by visiting the page in question and looking at the address that is displayed by your browser.
To delete a page, select the page that you wish to delete on the Carrelet control panel and click Go. You obviously want to check that you are deleting the right page: there is currently no 'undo' option, so all deletions are final!