The Pseudonym Pairs smart contract is fully implemented (source code), but, there is not yet a simple app client to "talk" to it. So, if you want to participate in testing it on the EthereumF Ropsten network it is probably necessary that you learn a bit of how Ethereum works, since you have to do some of the communication manually.
To opt-in to the test net, you just tell the contract to let you be part of it. You have to do that before the test net launches the first Pseudonym event. This first step of agreeing on a "genesis population" will require a bit of trust when the main net launches, but for the test net it will just accept anyone (which means technically bots could hijack the test net at genesis, but there is no profit resting on it so.. )
You command the contract 0x901e01E2d433ab5384A9bBc1C97714c35077D86E to let you opt-in with the command 0xd6074e14 that will invoke the function testNetFaucet(). This gives you a permit to register for the first event. Once that permit has been acquired, you command the contract to register you with 0x1aa3a008 that invokes register().
If you need test net ETH, use a faucet like https://faucet.ropsten.be/ or ask someone to send you some, or mine a few blocks.
That's it. Now you are registered for the first event on Saturday at 3 pm UTC. To read data from the contract, use a block explorer like Etherscan, https://ropsten.etherscan.io/address/0x901e01e2d433ab5384a9bbc1c97714c35077d86e#readContract.
To connect with likeminded people who want to collaborate around testing or proving the game theory of the Pseudonym Pairs system, open some social media channel. There is one on Telegram that could be used, https://t.me/pseudonympairs.
If PP works, it is the foundation of a "bit nation". Welcome to attempt to create it. /Johan