Where do I enable the iOS keychain on xamarin / vs?

I'm using xamarin forms and trying to use xamarin.Auth to save information in the device database..For android I did this and all right ... But when I squeeze IOS I get this error ...

> Xamarin.Auth.AccountStoreException: SaveAsync error = error = Could not save account to KeyChain: -34018
Add Empty Entitlements.plist 
 File /+ New file /+ iOS /+ Entitlements.plist
SecKeyChain.Add returned : -34018
1. Add Keychain Access Groups to the Entitlements file.
2. Turn on the Keychain Sharing switch in the Capabilities section in the app.

I'm using these lines in code behind:

        account.Properties.Add("teste2", "1");
        account.Properties.Add("teste1", "usereee");
        AccountStore.Create().Save(account, "clastech_montana");

That'sallI'vedonesofar...I'veresearchedalotandIdonotthinkIcanconnecttheioskeychainorifIdidsomethingwrong...itlookslikeIhavetocallmyiosdeveloperaccount...Iregisteredit,butdidnothavethecredentialsandidoptionthattheysaytheywouldhave.cansomeonehelp?!

There is no place to connect the key here