open command line and locate to the location of  keytool.exe.

import cert to keystore command:

keytool -importkeystore -srckeystore %certfileName% -srcstoretype PKCS12 -srcstorepass %CertFilePassword% -keystore %Thekeystore file that the cert will import to% -storepass %Thepassword will be used to read from keystore file.% -srcalias 1 -destalias %TheAliasNameUsedInKeystore file%

sample:
C:\Program Files\Java\jre1.8.0_91\bin>keytool.exe -importkeystore -srckeystore C:\MediaFirst\GetToken\tv3certossPerfA.pfx -srcstoretype PKCS12 -srcstorepass password -keystore C:\MediaFirst\Toos\JMRunner\Configs\MediaFirstApiTest.keystore -storepass password -srcalias 1 -destalias MediaFirstScale