After importing a certificate, you need to assign the certificate to keystore before it is used by Access Manager.
Click Security > Certificates.
Select a certificate.
Click Actions > Add Certificate to Keystores.
Specify the keystore to which you are adding the certificate. To locate a keystore:
Click Select Keystore.
For a description of the Access Manager keystores, see Access Manager Keystores.
For adding an external OAuth certificate, select the Signing keystore.
On the Keystore Details page, select the keystore, then click OK.
Specify the following details:
Alias: Specify the certificate alias.
Overwrite keys with same alias: Select whether to overwrite certificates with the same alias, if the alias you specify is already in use in that keystore.
Click OK.
Update the devices that are using this keystore.