Update templates

This extension uses fluid templates so you are able to override them like in most other TYPO3 extensions.

Override template using TypoScript

Do you have a site package? Put the templates into your site package extension. Otherwise you can put them into fileadmin if you really want.

plugin.tx_reserve {
  view {
    templateRootPaths >
    templateRootPaths {
      0 = EXT:reserve/Resources/Private/Templates/
      1 = EXT:site_package/Resources/Private/Extensions/reserve/Templates/
    }
    partialRootPaths >
    partialRootPaths {
      0 = EXT:reserve/Resources/Private/Partials/
      1 = EXT:site_package/Resources/Private/Extensions/reserve/Partials/
    }
    layoutRootPaths >
    layoutRootPaths {
      0 = EXT:reserve/Resources/Private/Layouts/
      1 = EXT:site_package/Resources/Private/Extensions/reserve/Layouts/
    }
  }
}

Override template using constant editor

TYPO3 Backend > Templates > Constant Editor

Constant editor