It is not too hard if you stop somewhere that has flights to Cuba.
You get a visa from the Cuban Embassy or Consulate, explaining why you want to visit. If you show that you have $$$, these are routinely granted. You also ask that the visa NOT be stamped into your passport. Poof. You are in Cuba. It is a beautiful place, but there is very little to do. Almost all of the tourist places are closed. You will be watched by your assigned secret police operative. Just don't be a smart ass and you will do fine.
Frankly, I think that keeping USA tourists out of Cuba is a mistake. The more contact with free people that the Cubans have, the faster the desire for freedom will grow.