Mapping two fields

Hi,

I have a field that is option set in the account entity. I would like to map this particular field to a field I created in the lead entity. The process would be: if I create a company that is already registered in the account entity, then, the field woudl be filled with the same value as the field in the account entity. I tried the 1:N Relationship but it doesn't work.

Thanks for the help!