Hey there, you should check out Help:Galleries, Slideshows, and Sliders. There's a bunch of different ways to get it working - so try it out first and let us know if you need any more help.
The best way to add one is in source edit mode and use the following help page as a reference: Help:Galleries, Slideshows, and Sliders/wikitext#Slider.
I don’t know how to do that on my wiki.
We don't know what your wiki is, so we can't help you anyway.
What do you think?