If you already have a results page on a different URL, you can adjust the plugin redirection to that URL on the General Options -> Logic & Behavior panel: https://i.imgur.com/cGgXpTr.png
If not: To have the search results page on a custom URL, but you must have a permalink strucure configured properly to tell WordPress how to resolve that URL. Here is a tutorial on how you can possibly do it: https://goo.gl/hG1UR
Before making any changes to the files suggested in that tutorial, I highly recommend backing up everything, and also consulting with a developer first, if you are not experienced in coding.
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