Multiply User Support

Only the post author/owner can edit/delete the post (admins in groups can delete posts too, but not edit them). You have to open a certain post so you can edit or delete it. All of your blog entries are listed in your Blog page (the analogous works for Reviews, Videos, etc):
http://YOUR_USERNAME.multiply.com/journal

and each item has an URL with a number, for example:
http://YOUR_USERNAME.multiply.com/journal/item/15/

Open the entry and you should be able to click on a link called edit or delete just below the post, to the left, so you make the modifications you want in that post or remove it completely.

You can also delete replies to your posts as well as delete posts in your Guestbook. If you don't know how to delete the comments in your Guestbook, take a look at this post:
http://usersupport.multiply.com/journal/item/131/Guestbook_FAQ

Sometimes when you add an entry to your Links section or save it as a draft you cannot open the entry to delete it. Try adding another entry and publish it, then you should be able to go to your Links page (yourusername.multiply.com/links) and delete the one you want.

There is also a post with a tip useful when you want to delete many posts:
http://usersupport.multiply.com/journal/item/153/How_to_Delete_Many_Posts_Faster

If you cannot find the edit/delete links in the posts you created, maybe the custom theme you are using removed it or make it invisible using the same color of your background or something else... If you think it's the problem, take a look at this post:
http://usersupport.multiply.com/journal/item/140/Using_a_Custom_Theme_Cannot_see_your_contentlinks_Read_this

If you cannot access the edit/delete link because you added a broken code to the entry, try this:
http://usersupport.multiply.com/journal/item/93/Editing_a_post_when_the_edit_link_doesnt_work