In the EveryAction API for Contact History, we are only able to see an ID field for the person who was responsible for the Contact Action. This field comes through as "Canvassed By" and shows an ID number (such as "2242207").
You will need to do a bit of work in EveryAction to determine which EveryAction user/canvasser is represented by the ID in question, but once you have determined which ID belongs to which user, you can use Data Transformations along with the Constituent ID in the Raiser's Edge to add a Solicitor record. See this video for more information.
Other knowledgebase articles that may be helpful include:
Can I import to existing Solicitor/Canvassers when I don't have their contact info in my data source?
How do I import when I only have the constituent id? - Last name is required!