From personal experience I must concur with the others saying "you can't". She or he can only decide for themselves that they enjoy Naturism.
My ex-wife of a twenty five year marriage started out as a Naturist but over the years lost interest to the point that she became somewhat intolerant of my own participation in the lifestyle. It was a primary reason we eventually divorced.
My present partner (10 years and running) is very anti-Naturism. Her opposition increased the more she came to realise how my belief in Naturism affected the way I wanted to live. I think at first she regarded it as an occasional holiday eccentricity, which to begin with she even participated in when we were alone together, for example in the garden pool or a hot tub. Now she pointedly refuses to meet me half way and even covers when coming out of the shower, which she never used to. It's like she's trying to set an example in the vain hope that it will rub off on me.
The weird thing is I am expected to be less Naturist in hers and her family's company than I would expect to be with people I don't even know.
It took little persuasion for her to use our simple garden pool in previous summers, so I will try to set that up again. Plus maybe invest in a hot tub. I think I merely half joking, told her costumes are not allowed in my pool and she didn't argue the point. Even though our garden is overlooked by immediate neighbours.
I live in hope (but not much) and wish all those with reluctant neighbours the best of luck. Re-compiling a lifetime of faulty programming is a daunting almost impossible task.