How to do second image on hover for mobile ?

[luxicy999]

I have tried various suggestions and it still doesnt work for mobile. Any help would be greatly appreciated, thank you very much! Oh and I would love some feedback on my site too!

my website is: luxicy999.com

[luxicy999]

i got it 

[Frisk]

Hello, how did you fix?

Also in your website I saw in all products page(eg rings) for each model you can see a preview of all photos present in the description, may I ask you how is called this functionality/add on?