So you create a Passle post. 

You share across your online networks. 

So far so good. 

BUT - you realise you really want to add/change the image on your post.  Easy to change on your post but what about Twitter?  They have already stored the old image and associated this with the post url and they are not picking up that you changed the image.  What can you do?

Here is what you must do to clear the cache on Twitter:

Go to Twitter Card Validator tool.  Simply insert the url of your Passle post to 'Card URL' and select 'Preview Card'. 

The Tweet preview should now show correctly with your updated image. Done.

What about LinkedIn?  Simple - to update the 'share image' on LinkedIn read following post from my colleague Lora: How to clear LinkedIn cache on my Passle posts