Email certificate problem

I have 2 certificates for emails. One was installed via browser and it works, but I had to import the other, because I had reinstalled and here is the problem.
I can not get it into Personal folder, it is stucked in Other People folder and email client gives this error, when I try to send an email. What should I do to fix it?
I tried to import it directly into Personal, I tried to find a way to delete certificates, but so far no luck, I am out of options here people. Can you please help me?