Unzip the download. The panorama variants contain one equirectangular EXR plus a PNG version; the cubemap variants contain six square faces. Blender: World tab in the Shader Editor, add an Environment Texture node, load the EXR and connect it to the Background input. Game engines: import the six cubemap faces as a skybox. The whole space series is on https://www.hdri-hub.com/shop/hdri/space