Yes you can. There are special e-mail addresses for the 3 first template categories:
to which you can send your items.
From each-email you send there, each line in the beginning of e-mail is added as a new item, up to the first empty line.
The items get added to the report of the user with the sender's From address. Use the same address to send your items that is your Weekdone login e-mail.
Make sure you have an empty line before your signature, otherwise each signature line gets added as an item as well.
The Subject line does not matter and is disregarded.