Image attachments on forum post

Hello,
which is the correct way to attach images png o jpg to a post here ??
I got always errors about library and size when I try to upload an image.

Image resize failed due to your image library not having support for this image type

Is there a kind of short tutorial to set environment correctly ?
Thanks

It’s a (reported) problem, as well with the impossibility to post code /code sections.

Thanks Albert … ;-(
Is it a vBullettin problem or the customizing not correct ?
Anyway we have to wait …
I think that do not have possibility to post images is really a urgent bug to fix