Unable to find manifest signing certificate in the certificate store.

[Dom]

I inherited a Console program written in CSharp. I'm trying to make
sense of it, so I tried to step through it in the debugger, but when I
do I get an error message:

"Unable to find manifest signing certificate in the certificate
store."

I pretty skilled in CSharp (though self-taught) but I really know
nothing about certificates. Can someone help me here? How do I get
around this? What does it do for me? How was it created?

TIA,
Dom