Hi,
could you please try to insert your .js files directly to the project folder? For example to the folder /CMSScripts/jquery/*
Uploading the file you created a document or media library file and it is not what you need.
Working with the jQuery requires
1. add a reference to jquery library (in Head section of masterpage)
2. add jquery method
3. create appropriate html code
A jquery example you can find for example in this
thread.
The slider web part is available in Kentico by default. Please take a look at Corporate site to the section /Examples/Web Parts/Listings and viewers/Documents/Content slider.
Best regards,
Ivana Tomanickova