First, if you want people to buy your yo-yos, you have to let them know what is for sale. The easiest way I can think of is to create a new thread (this is assuming you cannot walk up to your target audience and ask if they want your yo-yos). List what yo-yos you have, along with a reasonable asking price.
To post pictures, look between the subject line and body section (where you usually type). There is a button that inserts the pseudo-html your post needs to reference an image. Once you have a picture you want on your computer, go to a photo hosting site (tinypic, in your case), and upload a photo to your account. Copy the "direct link" to your photo, and paste it between the {img} and the {/img}.
When composing your post, the photo will look something like {img}www.hostwhoever.com/album/#01{/img}. It will have these brackets "[]"instead of these "{}".
For Paypal: go to Paypal dot com, and create a username and password. And link it up to your checking account. Or take a money order.
To ship... put the yo-yos in a padded envelope or (one of the free) flat-rate shipping boxes from your local post office. Write the address of the recipient in the center, and your address in the top left. Pay a few dollars, and it will be delivered to the recipient soon enough.
Also, read these:
http://www.yoyonation.com/talk/index.php/topic,57492.0.htmlhttp://www.yoyonation.com/talk/index.php/topic,57491.0.html-Jacob