Use this
insert into missinginfo ( mfname,mlname,id)
select 'john','wilson',id from account where username='abc@abc.com'
and if you want to insert multiple records then use this.
insert into missinginfo ( mfname,mlname,id)
select 'john','wilson',id from account where username='abc@abc.com'
union all
select 'john2','wilson2',id from account where username='abc@abc.com'