The Cuban Peso (CUP) will be the only local currency circulating as of January 1, 2021 with an official exchange rate of 24 CUP to the US dollar.
All goods and services in Cuba are priced and payable in Cuban Pesos (CUP).
The easiest place to change money is at CADECA (http://www.cadeca.cu/en/). Airports and Hotels have CADECA within their premises.
Credit Cards are accepted in most hotels and major shopping centers.