How to share a media topic in OK from another user?

Question

css

There is an application "N". When sharing this application through WidgetMediatopicPost, as we understand, the owner of this application is substituted in the post. Is there any way to substitute another participant? Let's add a developer and use his profile?

As I understand that for a share from another user, you need to use its access_token or session secret key

As I understand it, the following parameters are needed:
We use:
st.app={Application ID}
st.attachment={'Serialized jason'}
st.signature={ md5("st.attachment=" + attachment + secretKey);}

Well, what will secretKey be equal to? Application key?
st.access_token - ?

The user is added as a developer and you can generate access_token and session_secret_key