This system allows 1MB of attachment space per member. In My Controls you can see how many attachments you have, what space you have available, and if there were attachments in this screenshot, there would be check boxes for choosing attachments for download or deletion.
Uploading attachments for your posts or private messages is easy. You click the Upload button in the Attachments section of the message creation tools.
Next a window opens and you can find what you want to upload and click on it, the system will then upload the attachment, and when you post or send your private message, it will automatically be attached.
Note: Beehiveforum.US also allows each member 5MB of member space. You can find how to get your member space by reading the discussion How To: Member Web Space in the folder Member: Starting Out in this forum.