How to post pics.

How to post pics. I can't drag down uploads?

Pics must be resized to be 800 x 600 before uploading. Then use either the Go Advanced button below or the picture icon above to open the dialog for uploading pics. Limit is 6 pics per posting.

Don't have a clue, how to do that

What picture icon above?

In WEB version (not mobile)
when you click on reply it opens. a new window for you to enter text. Along the top of the window are icon buttons. These are, in order left to right (group 1) Switch to source mode, remove font (group 2) Paste[ as plain text] | bold, italicize, underline (group 3) font, size, color emoji (group 4) link, unlink, insert pic, insert viddy, |quote.
below the text input box to the far right is {Post Quick Reply} {Go Advanced} {Cancel}
To upload a picture that you have sized to 800x600 in some other app {edit photos} you can choose either the insert pic or the go advanced.
When you Go Advanced you will see a button below the text entry area {Manage Attachments} this will open a new window which will allow you to insert up to 6 pictures either inline or as attachments.
When you are done entering text and loading your pics you click the go button.