Do you need to download software to purchase ACT?
why should you download software , just buy in trading website
But let the coins sitting on exchanges not a good decision if anybody is long term investors than he should keep store the coins on a safe place where he has full control on private keys. It is good to download to official wallet and store these coins.
The most safe and convenient mobile wallet to hold ACT is Kcash, which also support dozen of other major cryptocurrency.
You can download it from following website:
https://www.kcash.com/