When creating a spot UV job, You must include a spot UV pdf along with the regular full colour pdf. The spot UV pdf is used to show where the UV will be placed. The CMYK pdf and the spot UV must be separate files.

Professionally Designed Business Card - Design Creative Media - Vancouver Graphic Designer

Normal CMYK file

Professionally Designed Business Card With Spot UV Gloss Mask - Design Creative Media - Vancouver Graphic Designer

Spot UV file

Use 100% black to indicate where you would like the UV gloss.
White will indicate no UV.