Start up a Sandbox game starting in the Colonial Era. (If you don’t have the Watch The World Burn achievement yet, set the win condition to advance to World Wars Era.) Start with $200k treasury, 50 population, and lower the difficulty.
Buy the upgrade for the Palace (4 more troops) and build at least one - I built 2 - Forts. Max the budgets and wait for the job slots to be filled.
If the Revolutionaries send you any requests, complete them, and take the “10 Revolutionary immigrants” reward. These should be easy requests like build a tavern, produce 1000 corn, etc.
Go into your Almanac, then find your list of Royalists. Pay $3k to put a Kill order on as many of them as you can. Your soldiers will seek them out and kill them automatically.
Gradually repeat these processes, accumulating more Revolutionary immigrants on Tropico by completing requests, and killing the Royalists who show up on each freighter. Eventually the achievement will unlock.
I had 80 Revolutionaries, something like 2 Royalists, and a total population of 112 when it popped.