Most of the events in the blogosphere require reposting when you wish to send in already posted dishes for the event. To repost you need to -
1. First add a link to the event announcement in the original post that you have posted earlier.
2. Go to your latest post and add something like this to it -
"Reposting Onion pakoda for EC's WYF:Tea time snack event"
Provide a link to onion pakoda (the link to the recipe on your blog) and WYF:Tea time snack event (the link to event announcement)
You can add the photo of your dish also here (onion pakoda in this example)..
For help on adding link, refer to this post - How to add a link to the post