Due it is not easy to find in the docs of AWS, i’m will post it here to easier find it.
You need the aws-commandline tool for it. It must be configured with an account with FullAccess to Cloudfront.
After this you can add the Cert with this command:
aws iam upload-server-certificate --server-certificate-name ShowNameForTheCert --certificate-body file://publickey.crt --private-key file://privatekey.key --certificate-chain file://chain.ca-bundle --path=/cloudfront/
After you ran this command successfully, you can select the cert in the cloudfront configuration.