Firstly open up the will you want i.e State items. like this.
Then look at the bottom number e.g. mine is 2512 and memorize it. now go to the images you want adding e.g. and rename them to 2513 2514 ect depending on how many there are. also put the items you want in a folder on there own like in this picture. (dont need the placements for items only for weps n arms ect)
Now goto import all then Select the add option and click the folder where your new items are and then click ok and click import