Set up a "rollover IRA" with an online brokerage. Shop around for new account bonuses and low transaction costs.
Contact customer service of your new brokerage. Ask for specific instructions to roll over your 401k without incurring taxes.
Follow their instructions. On every call, emphasize that you are doing a rollover and do not want to incur taxes.
Once the money is in your new account, buy as many shares of VTI as you can. Then set dividends to reinvest (may be called a DRIP in their system).
Next, leave this account alone.