How to specify region for shards in MongoDB Atlas. Also how to appropriately set 2 shard for a cluster

I'm trying to create 2 shard for a single cluster in MongoDB atlas.I need to set zone for each shard , so that docs with
shard-key region is saved to respective shard. I need to make sure that each Shard is located in the specified region.How to setup shards and specify the region (location of the server) for the shard and add corresponding region code as zone for the shard in MongoDB Atlas.