First, you may need to create the ai you are going to set the bot to.
Use
/botai add spin spin
This will create an ai with the name "spin" that uses only the "spin" instruction.
If you want a different speed or type of spin, read the help: /help botai spin
Then use the extra arguments with /botai add spin spin [interval] [speed]
Then apply it to the bot you want:
Use
/botset [botname] spin
If you are not playing on your own server, or don't have permission to add bot ai, you might have to ask staff to do it or find an already-added ai that uses spin.