The eRequest Business Central Application is available on the Business Central App Source here
https://appsource.microsoft.com/en-gb/product/dynamics-365-business-central/pubid.nolanbusinesssolutionsplc1635777129432%7Caid.erequest%7Cpappid.5dc61188-5dbb-472f-b7c4-f21a3cc227f9?tab=overview
Follow the standard Business Central extension install.