1- You need a wallet. Download MetaMask to create a wallet. 

MetaMask
Uniswap

2- Obtain DDI by swapping Ethereum for DDI using Uniswap.

Note: Ensure DDI Token address for the swap is:
0xD3caeCab1663ccF26ced842cFa73BB1bB3A05029

3- Check the ownership of DDI on Etherscan

Etherscan
DDI

4- Use your DDI toward democratic activities