While you can bring your own .app or .ipsw files when creating VMs, we allow you to specify anka create -a latest to target the latest macOS or anka create -a VERSION where VERSION is the specific macOS version. To get a list of macOS versions available, see anka create --list:
bash$ anka create -l
+---------------+---------+----------------------+
| version | build | post_date |
+---------------+---------+----------------------+
| 11.7.2 | 20G1020 | Dec 13 13:14:48 2022 |
+---------------+---------+----------------------+
| 12.6.2 | 21G320 | Dec 13 13:13:39 2022 |
+---------------+---------+----------------------+
| 13.1 (latest) | 22C65 | Dec 13 13:08:36 2022 |
+---------------+---------+----------------------+
| 13.0.1 | 22A400 | Nov 9 13:02:34 2022 |
. . .
bash$ anka create -a 11.7.2 11.7.2
75% [||||||||||||||||||||||||||||||||||||||||||||| ] 16:15 ETA