You can try something like:
insert into database1.dbo.tablename
select * from database2.dbo.tablename
Or if the databases are on different SQL servers:
insert into server1.database1.dbo.tablename
select * from server2.database2.dbo.tablename
If the table has a different name, you simply specify that in your SQL query. And if you have different fields (or an identity field), you just specify the actual field name instead of just using the *.