You can do so by emailing your Qik video link to post@posterous.com. Enter the title of the post in the email subject line and put the link in the email body. Posterous will automatically embed that video in the blog.   

Alternatively, you are able to embed your videos by yourself with the following steps:

1) Log in to Qik at http://qik.com

2) Click on 'My Videos' and select the specific video you would like to embed

3) On the video screen, at the bottom right, there is an option 'Menu' which allows you to copy the embed html code

4) Log into Posterous and select the post which you would like to embed in

5) Click on the 'html' icon and and paste the code in the provided box

6) Update your post and check that the video has been embedded correctly on your blog