To fetch sequences from the BLAST database do the following:
Open Tools ‣ BLAST ‣ BLAST query database.
The Fetch Sequence from BLAST database dialog will appear. It fetch sequences by 'id' from 'blast result' context menu item of the blast result.
Here you need to select a query ID, database, type of file(s) and output path. After that click on the Fetch button. To fetch sequences for several annotations at the same time select the blast results with Ctrl key and call the Fetch sequences from local BLAST database->Fetch sequences by 'id' from 'blast result' context menu item.