Hi MH,
In my game, Welling doesn't have a third kit. If you want them to have one, you will have to create the in-match version using the Data Editor. If you don't already have it, you can get it free from Steam. But - to my knowledge at least - you can't do this mid-save, because it involves altering the database that you then tell the game to use when it creates your new game for the first time.
Your images are called home ; away ; third. I'd recommend calling them welling_1.png ; welling_2.png ; welling_3.png. Then the three lines for the relevant config file should be:
<record from="welling_1" to="graphics/pictures/team/733/kits/home"/>
<record from="welling_2" to="graphics/pictures/team/733/kits/away"/>
<record from="welling_3" to="graphics/pictures/team/733/kits/third"/>
I tested the home one on my game and it went in OK, but your images are only 200 x 200 pixels - 220 x 220 is the norm. There's no harm in putting all three images into the folder and config file. If the third kit option is not activated in your database file, the game will ignore the third image.