Hi! You habe to use the MAP-function. Click on properties to put the "covering" paralel with th fuselage. (head = 90 deg.)
Keep th property diag open, just pull it out of the way, you will need it during the covering prosedure. Wings needs pitch = 90 deg, and head set back to 0.
After this you have to scale and move 'till you got the right pattern in the right place.
btw: you don't have to use 256X256 pixles, it's no problem making it larger, but you must use 256, 512, 1024 in square. Lager resolution gives more details, and of course larger files.
The manual in Metasequoia home page sholud give enough instructions.
G

d luck!