Register digital signature

Hello,

I want to register digital signature of a director in MCA website.

after filling up all the details and giving submit, the site provides the space for selecting digital signature and give email ID.

when i click select digital signature tab it displays the following Msg

"certificate has not been selected. To complete the process pls select the certificate".

i have all the preriquiste software for filing in MCA.

kindly help me.