Hypothetically, I would say;
STEP 1 Grow the community, engage in vigourous intellectual debate to generate a consencious around a robust, clearly thought out, logically consistent feasable CS plan or manifesto.
STEP 2 Form a corporation to develop the key enabling technologies and methodolies identified by the CS plan as well as identify the key technological partners for the future and attract financing to the idea until such time as the appropriate TRL is reached.
STEP 3 Identify the key geographic requirements as set out in the CS plan and then produce a short list identifying all eligable sites worldwide and begin eplorative negotiations with the respective governments regarding land prices, sovereignty and govermental investment, to identify the best alround deal. Launch a full scale multibillion dollar funding round to secure investment from the IMF, the world bank, etc.
STEP 4 Build it.
STEP 5 They will come.