I've done this successfully several times and it was a little fidgety. But this is how I did it (from memory):
1. Reset the Remote Control to factory default
2. Reset the Spark to factory default
3. Use 12341234 as Remote password
4. Use DJI Assistant software to obtain Spark password
5. Connect phone to Spark's wifi
6. Connect phone to Remote's wifi
Then you power everything down and restart. Now the phone, remote and Spark should all be connected.
Sometimes it works on first try. Sometimes I needed a second go round.
Best of luck to you