After you click on "Create Gallery", just fill in the information that is requested- at least as much as you want to complete. ;-) This is your "User Profile" for the Gallery. If I remember correctly, this then takes you to the "Manage Gallery" page.
Once in the "Manage Gallery" area, click on the "Create ALBUM" link in the upper-left purple box. Fill out the info for your vehicle and click on the button at the bottom of the screen that says "CREATE ALBUM". This will take you back to the "Manage Gallery" screen. You should see your album title listed on the left. Click the album and it takes you to the "EDIT Album" page.
On the "Edit Album" page, scroll down to the bottom of the page and you should see a line that says "Add Photo To Album". Just under this text is a box with "BROWSE" and "UPLOAD" buttons next to it. If you know where on your hard drive the file is located, just type the path into the box (an example is c:\temp\mytruckpic). Otherwise, click on the "BROWSE" button and it will pop up a window showing information on your local hard drive. If you have a picture of your truck in (again- only an example) c:\temp, then change to c:\temp and click on the file you want to upload. Then click "OK". This will take you back to the web page and you should see "C:\temp\truckpicture" in the box.
Now, click on the "UPLOAD" button. Copying your picture to the Gallery can take a little while- depending on your picture size and the speed of your Internet connection. When the picture has finished uploading, you'll be taken back to the "Edit Album" page. Scroll down to the bottom and you should see your picture. Do this again to add another picture to the album. You can create multiple albums too! :-)