Problem with creating the certificate. HELP!!

[serv...@gmail.com]

Hey, guys i dont have a mac, and I'm building this on a ubuntu computer and then my server will be a debian machine, how can i create the certificate from ubuntu i have created the .csr and the .key file from  my computer, and i did upload the .csr to the apple page to create the certificate, it was created but now i only have a .cer certificate, and all the tutorial i've seen they only show how to make p12 files on a mac machine, but i dont have a mac, how can i prepare the files on a ubuntu machine???

PLEASE HELP!!! 

thanks in advance.

[tom.f...@gmail.com]

openssl genrsa -out server.key 2048

openssl req -new -key server.key -out server.csr

// for the key

openssl x509 -in aps_development.cer -inform der -out PushChatCert.pem

// combine to bundle

cat PushChatCert.pem server.key >> bundle.pem