To customize the partner-facing lead phases in your portal, you'll need to access the Leads sub-tab under your Accounts & Settings in your CRM.
From there, you can customize your lead registration form by scrolling to the bottom to the Lead Phases section and selecting the pencil icon to edit.
Keep in mind that once a lead phase is added and saved, it cannot be removed due to possible connections with existing leads. However, you can always revert to the original phases (Processing, Prospecting, Consulting, Proposed) if needed. Please note, a Closed Lost phase can trigger your PartnerPortal.io leads to expire if you'd like.