You will find the. apk file in your my/files - downloads there you will have to tap it to launch the installer.
Note, you have to allow your device to install apps from unknown sources if it prompts you to do so or says unable to install.
Also keep in mind that the file might need more space to decompress. I found that to be a big issue while installing vn's on Android, not always but mostly when you don't have a lot of storage space left.
Hope this helps