Registering an import....

I've just bought an ST70 that was imported from Denmark a few years ago but wasn't registered here.
I don't have a registration doc, just the bill of sale and an export doc.
With these i've managed to get a Nova so now it's on to Dvla.
Does anyone know the steps i have to go thru to get it registered?
It's a 1979 model.
Any help appreciated, Thanks,
Andyfitz