Open your file partcombinationdesc.xml located in your "character" folder.
Using CTRL+F, locate the PAC file name of the armor you want to put wings.
For example, if I want to put wings to the Valkyrie's Aker Guard Armor, I should search for the FIRST declaration of "PVW_00_UB_0052.PAC"
<!-- Valkyrie Aker Guard -->
<Upperbody MeshFileName="1_PC/7_PVW/ARMOR/9_UPPERBODY/PVW_00_UB_0052.PAC">
<Lowerbody MeshFileName="1_PC/7_PVW/ARMOR/10_LOWERBODY/PVW_00_LB_0052.PAC"/>
<Hand MeshFileName="1_PC/7_PVW/ARMOR/11_HAND/PVW_00_HAND_0052.PAC"/>
<Foot MeshFileName="1_PC/7_PVW/ARMOR/12_FOOT/PVW_00_FOOT_0052.PAC"/>
<Helm MeshFileName="1_PC/7_PVW/ARMOR/13_HEL/PVW_00_HEL_0052.PAC"/>
<Shoulder MeshFileName="1_PC/7_PVW/ARMOR/14_SHO/PVW_00_SHO_0052.PAC"/>
<Cloak MeshFileName="1_PC/7_PVW/ARMOR/19_CLOAK/PVW_00_CLOAK_0052.PAC"/>
</Upperbody>
Now add the following line to before the "</Upperbody>":
<Item_hair MeshFileName = "1_PC/7_PVW/ARMOR/14_SHO/PVW_00_SHO_0034.PAC"/>
Remember to use the right class prefix for your class, since we are doing this for Valkyrie, I'm using 7_PVW and PVW.
After that save the file and you should be good to go.