This really becomes a programming question because both tools have a web API, so you just need to be able to interface with them. Splunk uses a REST API but has a good development kit to make things easier, and Archer uses a SOAP API.
A good place to start is the Splunk SDK:
http://dev.splunk.com/view/sdks/SP-CAAADP7
And here is the Archer documentation:
https://community.emc.com/community/connect/grc_ecosystem/rsa_archer
Adding records to Archer is slightly more complicated than pulling them out of Splunk, but essentially you just create a session token (general.CreateUserSessionFromInstance) and then add a record (record.CreateRecord) with your fields.
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