Is there any way how can I integrate Hot Editor into SMF?
Sure, if you don't mind rewriting Subs-Editor.php to support safe, secure conversion of HTML to bbcode (see html_to_bbc, bbc_to_html, legalise_bbc in Subs-Editor, all will need to be rewritten)
Well, I don't how time to do that by myself right know, so can someone provide me the instructions for this?
No, because no-one's done it. In fact, no-one that I know has bridged a different WYSIWYG editor safely/securely with SMF 2.0 (except possibly Orstio, who bridged TinyMCE with SMF, except that he might have done it with 1.1.x)