Once you create a profile on the site you could then search for other members in your location selecting Widowed as the relationship status you are interested in finding.
They have a very large membership base so I am sure you will find some singles with that status at I paid for a three month membership and got many "wants to meet you" notices. I even saw some people with more than 1 profile..time fraud and hardly anyone in my area either...first one that reached out to me was saying he lived in Syria but would be in US soon and willing to relocate... Not sure about the authenticity of dating websites for widowers, but wants to share a suggestion that you should try some other good websites that are not involved in fraud and allow widowers to make their profiles on them, because mainly people look for the website that is reliable either for the one that is specialized in a particular field.
One other option I just thought of you could try would be
With their profiles they do have a relationship status of "Widowed".
As a recent divorcee, he had begun a new relationship with a widow and at the time they dated, thought that he had finally found “the one.” He felt like his ex-wife was never really his soul mate and that his soul mate was still out there, and it was Terry (also a fake name to protect identities).