When I’m asked this question in an in-person conversation, I find that I can give a better answer if I first find out more about what the person asking the question thinks about divine action in other parts of the natural world. So I might ask questions like these: What do you think God is doing when robins hunt for worms to feed their young? What do you think God is doing to make the sun shine? What is God doing to make the rain fall where it falls? Do you think God controls where every single molecule goes on every snowflake, and if so, how? What is God doing when a child grows from a single fertilized cell to a newborn infant? People could give a variety of answers to those questions, and based on their answers, I can better answer them regarding what I think God is doing in biological evolution.
When I’m answering that question in writing (rather than an in-person conversation), I might write someting like the following list:
“God designed the fundamental laws and conditions of creation. God gave existence to creation. God sustains and concurs with the natural laws he created – natural laws which include both deterministic and random processes. God might have selected the outcomes of particular random events to guide natural history down particular paths. God can do miracles, and might have performed miracles at various points in natural history, although it is unwise to look at every gap in current scientific explanations as evidence of supernatural miracles. At some point in human history, God began to give special revelation to human beings in various ways.”
Each one of those sentences is worth paragraphs of clarification, but for that clarification, I’d ask you to check out some things I’ve already writen. I also highly recommend Robert Bishop’s essay at BioLogos on “Recovering the Doctrine of Creation”.