How can i exec sp_xp_cmdshell_proxy_account

SQL Server Administration
1

Dear All,

I give some users to check my hard drive space MS SQL Server. But they are have no sysadmin permission.

and then I try to execute as below command:

EXEC sp_xp_cmdshell_proxy_account 'PC\12520', '123';

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It still not work.
Please help provide me step to do this.