Here’s a link to the E-SIGN Act: https://www.gpo.gov/fdsys/pkg/PLAW-106publ229/pdf/PLAW-106publ229.pdf. Take a look at 101(c).
Generally, you need to provide notice of rights and certain inforamtion prior to consent, provide information on hard/software prior to consent, and document consent to obtain the documents in an electronic format and demonstrate that the consumer can receive/obtain the documents in the format you will use.
Maybe others will weigh in on how they accomplish this:)