How should i start the Proposal Party?

Like an engagement party? but announcing the wedding date and details? i'd start with your budget, theme and must haves. will you serve a meal, hord'uerves? sweets?

Are you referring to an engagement party or to propose to your bridesmaids / groomsman?

Meaning, an engagement party? I would first figure out guest list and budget, and then look at a venue that can hold all of the people you plan to invite. Restaurants that have private rooms are great for smaller groups, or you can host it at someone's house. From there, figure out what food you'd like to serve (full meal? appetizers? snacks? dessert?), theme/decorations, invitations, and any other details.

I've never heard of a proposal party. It sounds similar to an engagement party? We've been to a few of those. Typically the bride or groom's parents host it at their home and there is food, drinks, music, pictures of the bride & groom, and mingling. It's always pretty lowkey but typically happens 1-3 months after they get engaged.