If you don't want to add a Gallery (called Media Album here), you can use the "Upload a File" button next to the "Post Reply" button. There are image size restrictions, the need to be maximum size 1600 x 1600 pixels and under 1MB.
If you do want to add an image to the Gallery, see the images attached here...
These are just thumbnails, click to view larger so you can read them
Yours might look a little different if you are using the White default background (I find black kinder to my eyes).
If you go to the menu under the HIVEWIRE3D logo, there is HOME, FORUM, MEDIA, RESOURSES, and MEMBERS. Go to Media, that is where you will find peoples images that they may not have put into a particular thread (it does help to have your images in the Albums because if you want to put it into more than one thread you don't have to upload multiple times).
On the Right at the top is a button to "Add Media", if you click that it will take you to a new page, it will ask for an Album, you can create a new category (for example, I have a Horse album I put all my horse images, I have a Dusk/Dawn one, and Animal one, a People one etc). Then it will ask for an image to upload, click button, search for your image and select the one you want on your hard drive. There are extra fields to change the name of your photo, add a description and tags etc. Just follow the prompts