How to change url in sagepay plugin

My website payment plugin is about to fail due to be pointing at an old url. How can i change the url to the new one please

Dear Martin,

Thank you for submitting the request here. You are using older version of EShop Sagepay payment plugin. Please go to My Downloads section to re-download it again, then update it to your site, then the problem will be resolved.

I hope this is useful.

Sincerely, Giang