Automaticallly set Consent Status to OptIn

Hi,

I have a Web2Lead form set up in Wordpress Gravity forms, so when someone submits the form, they are added as a lead to then receive Marketing emails. 

However, since the default value is Null, we have to manually set each new Lead's Consent Status to Opt In to get the emails.

I cant figure out how to connect the Consent Status field to the form, or a way of having Opt In as the default value.

Any help would be greatly appreciated.

Thanks.