If your Benno Boost is the model year 2019 or earlier (Boost EVO 3, 2 or 1), then you will need the Benno Platform Cargo Rail (55cm x 68cm). To install the Cargo Rail, you will also need this rail clamp set. To install the clamps, visit the installation manual. Then, to install the Cargo Rail, take a look at this manual. (It's recommended to have a mechanic at an authorized Benno dealer install these parts.)
If your Boost is the year 2020 and later (Boost EVO 4 or later), it will require the Benno Platform Cargo Rail Plus (55cm x 72cm). To install the Cargo Rail Plus, you will also need the Rail Clamp Set Plus. To install the clamps, read this manual. Then, to install the Cargo Rail Plus, take a look at these instructions. (It's recommended to have a mechanic at an authorized Benno dealer install these parts.)