Read the DMV notice, put a qualifying policy in force, have the insurer file the certificate where required, pay the reinstatement fee the DMV publishes, satisfy any court conditions, and keep the policy in force for the full proof period.
More detail
The order matters more than the list. The notice comes first because it is the only document that states your specific conditions. The policy comes second because, where the DMV lists proof of financial responsibility as a requirement, the state will not complete a reinstatement while waiting on it, and the DMV also requires an SR-22 on file during an interlock permit when the vehicle is registered in the driver's name only. The fee and any testing or documentation follow. Keeping the policy in force is not a step so much as the condition of everything else staying done. Two things that are not steps but feel like them: waiting for the court case to close, which does not advance the DMV track, and calling the DMV repeatedly to check status, which is less productive than confirming with the producer that the certificate actually transmitted.