You put the skin in the campaign/CampaignData/skins folder and the naming convention is very specific.
"Off_Aviatik_BI_ace_t_FFA 8b 1915_Axel Leidenbrock.dds" Replacing "Axel Leidenbrock" with whatever particular name you want. Note the spaces as well as underscores.
Last edited by Maeran; 06/12/1511:10 PM. Reason: edited for precision and silly typos