Actually it is quite simple - read the posts here at https://www.gt-rider.com/thailand-motorcycle-forum/simple-way-to-post-photo-s-on-gt-rider-t5866.html and also at https://www.gt-rider.com/thailand-motorcycle-forum/adding-pictures-help-t1167.html
Most important to know is that the photos must be stored somewhere already, be it on your own website or on other sites such as Imageschack (http://www.imageshack.us/), Photobucket (http://photobucket.com/), etc.
This will not work as you don't have the end image statement for the first picture but instead have two end image statement at the end of the second picture [/img]/IMG]
This is how it should be:
In case you want to have space in between the pictures just enter a space or use a hard return (ENTER) to separate the pictures
With regard to the video I can't help as I have never used this on the forum. I do know that there are buttons on the top of the page to insert video's stored on Photobucket and My Tube. I guess you have the copy the URL from the embed code on the Photobucket site in between the two [photobucket:verjx8gg][/photobucket:verjx8gg] statements. Maybe someone else can help with this.