Just click download button to last page of Couch to 5K® Mod App. Then you can download Mod APK file.
If the file you download is HappyMod App, that means the file is an XAPK file. It cannot be installed directly on your Android Devices. You need download the HappyMod first. Then you back the webpage, click download button, this app will be downloaded on HappyMod App.
The download speed in HappyMod App is always fast. If you download speed is slow, you can pause the download progress, wait for minutes, then restart the download, the download speed will faster.
There are some of reasons the download is not start. You can try several times.