Stash cannot DRS transfer, but they can transfer to another broker (potentially for a $75 fee). A popular choice is Fidelity, who can DRS transfer for free, and quickly. They have also been known to reimburse the transfer fee if asked (up to $75).
Stash to Fidelity Route:
Open an account with Fidelity. When it asks you how you want to fund your account, select transfer from another brokerage. Fidelity will pull your shares from Stash. This will take roughly 3 days. From there you can follow the Fidelity guide located here.