Mary,
Yes, you'd have the Account table's PrimaryKey in the Phone table as a foriegn key. The phone table could have the phone# itself be the primary key of that table, but then you couldn't have a phone number belong to more than one account--which could be the case, say if one of the account's phone #'s was a company phone, and other accounts used that same phone#.
Two ways around that--First, the easy way, just make some other field be the key of the phone table, such as a sequential number--now you won't be 'normalized', but that's not the end of the world.
Second, the right way (but more complex when it comes to the query logic), is to have an intermediate table between the phone & Account table. If you want more info on that, let me know. Many people choose the first way, it's really not a bad way to go.
--Jim