You can automate it. Essentially, what happens is the contributions get sent to DPSP and then transferred into the brokerage link account. You can set this up under the contributions tab on the 401k.com website. It can be slightly confusing at first, so I recommend calling fidelity to help set it up on the first go around, they’re always extremely helpful.

Once the money is in the brokerage link, those transactions will need to them happen manually. So if you want to buy an ETF or stock you would make those purchase at intervals of your choosing. When the money isn’t invested it sits in the account, essentially, as cash.