You can create a partition on the multipath device, optionally create a file system on the namespace, and mount the partition.
# multipath -ll
The result of this command shows two devices, dm-19 and dm-16 :
eui.00001ffe5a94ff8500a0980000af4444 dm-19 NVME,Lenovo DE-Series
size=10G features='1 queue_if_no_path' hwhandler='0' wp=rw
|-+- policy='service-time 0' prio=8 status=active
| |- #:#:#:# nvme0n19 259:19 active ready running
| `- #:#:#:# nvme1n19 259:115 active ready running
`-+- policy='service-time 0' prio=2 status=enabled
|- #:#:#:# nvme2n19 259:51 active ready running
`- #:#:#:# nvme3n19 259:83 active ready running
eui.00001fd25a94fef000a0980000af4444 dm-16 NVME,Lenovo DE-Series
size=16G features='1 queue_if_no_path' hwhandler='0' wp=rw
|-+- policy='service-time 0' prio=8 status=active
| |- #:#:#:# nvme0n16 259:16 active ready running
| `- #:#:#:# nvme1n16 259:112 active ready running
`-+- policy='service-time 0' prio=2 status=enabled
|- #:#:#:# nvme2n16 259:48 active ready running
`- #:#:#:# nvme3n16 259:80 active ready running
# mkfs.ext4 /dev/mapper/dm-19
mke2fs 1.42.11 (09-Jul-2014)
Creating filesystem with 2620928 4k blocks and 655360 inodes
Filesystem UUID: 97f987e9-47b8-47f7-b434-bf3ebbe826d0
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
# mkdir /mnt/ext4
# mount /dev/mapper/eui.00001ffe5a94ff8500a0980000af4444 /mnt/ext4