Use the verb grant_privs to grant a user access to a named credential.
emcli grant_privs -name=MARY -privilege="GET_CREDENTIAL;CRED_NAME=HOST-CREDS:CRED_OWNER=SCOTT"
..grants the user MARY view privileges on the credentials called HOST-CREDS owned by SCOTT.
View privileges will allow Mary to use the credentials but will not allow her to see sensitive information such as the password.
Check out the security doc for more information on named credentials
Other privileges you can grant to credentials are FULL_CREDENTIAL and EDIT_CREDENTIAL.
Check out the EMCLI reference guide for more details on grant_privs verb: