To configure quicken to access your Vanguard accounts is quite simple - initially.
Let quicken know you want to add a new account, type in Vanguard Group as the institution and it will offer to download the account data from Vanguard. However, you also need to now your account numbers - especially if you're already created the accounts in Quicken. Specifically - which account is which.
Quicken will download the list of accounts and ask you to associate them with existing accounts or select new accounts. Oddly, Quicken did not offer to set-up my son's 529 account. I'll have to ask Vanguard why.
I have a non-retirement brokerage account with Vanguard. My primary purpose is to use it for Vanguard funds. The brokerage fees are ridiculous - $35 per transaction - compare that to first trade at $6.99 or so. However, Vanguard does set-up two accounts for you to download, so Quicken must also have two accounts (not one - even if you, like I, think of them as one). You need one account for the Vanguard non-retirement mutual funds and the other quicken account will act as your vanguard non-retirement brokerage account (for things other than their mutual funds). Kind of tricky.
Bottom line, if you have the brokerage feature, plan on setting up two accounts in quicken.