Hi @charliev,
You may attach a file by clicking the upload arrow (7th icon from the left at the top of the Reply window)
and follow the on screen directions to submit your material. If the file is larger than the maximum size of 3 mb, use a file sharing service such as Google Drive or Dropbox and include the appropriate url with your post to locate the file.
Here are a few links to address the clipping issue.
Clipping Plane 1
Clipping Plane 2
Clipping Plane 3
Clipping Plane 4
Clipping Plane 5
Good luck