To join the Alpha Test of HeroesTD, first access to the following link:

Then follow the below instructions:

STEP 1: Access to the above link, then sign in the email you have registered for the Alpha Test

STEP 2: Download the Alpha Test App on Google Play by accessing to the following links:

STEP 3: Install the app, when the downloading is finished, you can enjoy HeroesTD right then.

For further detaited tutorial, you can take reference from the below tutorial video: