I use Smugmug for all my RV-7 picture posting to VAF. Make sure, after you click the "share" icon, look for where it says "Choose a size" and choose one. I usually go with "Large". The resulting link displayed in the box below should end in .jpg, which is what you want to use here.
You'll need to copy-and-paste (Ctrl-C / Ctrl-V) that URL between two "IMG" tags when typing, or when composing a post you can click on the photo icon above the text-entry box, and paste the URL string into that and the forum will automatically include the IMG tags for you.
With BBCode (the stuff that runs DR's forums for him), "tags" are things that alter what you've typed into bold text, italicised, hyperlinks or photos. They are used by enclosing them between [] brackets such as: [image] <your fancy URL address> [/image]
would in turn embed your photo into your post if you used 'IMG' instead of the word image.
Ok this works for me every time. In smugmug do as Draker did BUT after picking size next click the box BBCODE. COPY the code that shows up in the box by whatever means you like ( highlight hover over copy with apple iOS or control c if highlighted with windows) . After copying of code go to your post on VAF and put cursor where to insert. Then click on fifth icon from right..looks like a box with mountain and sun in it....another box will open up .....remove the http code in the box and do a paste.....your code from smugmug will go into the box ....ENTER ....now do a preview a nd your pic should be there.