Create table partitions on different filegroups, the first boundary on a Memory Optimised filegroup
Partitioning memory-optimized tables directly is not yet supported. See SQL Server Features Not Supported for In-Memory OLTP.

A workaround is described in the documentation Application Pattern for Partitioning Memory-Optimized Tables


  You can emulate partitioned tables with memory-optimized tables by maintaining a partitioned table and a memory-optimized table with a common schema. Current data would be inserted and updated in the memory-optimized table, while less-frequently accessed data would be maintained in the traditional partitioned table.


Alternatively, you could consider other technology solutions like Columnstore for real time operational analytics, which combines in-memory OLTP with columnstore (as [optionally filtered] secondary storage).