you forgot to join the Login table so:
insert into Accused(FirID,Name,FatherName,Gender,Phone,Address,Alias,NIC,Age)
select FirID,'farooq','farooq','farooq' ,'farooq' ,'farooq','farooq','farooq','farooq'
FROM Fir as f
inner join Login as l on l.UserID = f.UserID
WHERE l.UserName ='Aman'