Travelers must present a travel authorization obtained before departure at www.travel.gov.sl.
On arrival at Freetown Lungi International airport, all passengers are required to have both a COVID-19 PCR and RDT test, at their own expense. Travelers will be allowed to leave the airport and travel if the RDT test is negative, while waiting for the result of the PCR test for no more than 48 hours.
Children under the age of 2 are exempt from presenting a COVID-19 test.
Travelers with proof of recovery from the virus within the last 90 days prior to boarding. Proof of a recent positive viral test and a letter from your healthcare provider or a public health official stating that you were cleared to travel.
More info at the CDC site
Travelers who did not get tested, are advised to stay home and self-quarantine for 10 days after travel.