How do I change a point (node) to an area (way)?

In Potlatch 2, you can click on the node, then Shift-click, and it will turn the node into a rectangular way with all the tags intact.

If you only want to transfer the tags from existing node to existing way and leave the node intact, you could first transfer the tags to another node, then create that into an way, then copy the tags from that way to the existing one. Stepwise:

1. Click on existing node with tags
2. Create new node
3. Press R while on new node to transfer tags from existing node to new node
4. Shift-click to create new way from new node
5. Click on existing way
6. Press R to transfer tags from new way to existing way
7. Delete new way

This really depends on the editor you are using, which you don't mention. In JOSM you can copy the tags of any object to a new one (Ctrl+Shift+V), in other editors it may not be possible. I currently don't know of any editor that allows you to "expand" a node in to a way, so typically you will draw a new polygon/area and copy the tags to that, worst case one by one.

not sure what you mean by this "In the tag popup there are not only the nine tags for the point, but five things listed above the tags, "Facilities...", "Man Made...", "Annotation..." etc."

But here is how I would do it using JOSM:
draw the outline of the cafe using the node drawing tool,
click off (select the select tool and click on the background ie not on an object),
select your node with all the tags on using the select tool, select Edit, Copy from the top menu,
select the new building outline you drew and select Edit, Paste Tags from the top menu,
check tags seem suitable, select your old node and delete.
Probably best to read the Help in JOSM to get familiar with this editor first.
I found the most important think I needed to know was to "click off" after doing each object draw.

It is also very helpful to tick Layers and Tags/Memberships under the Windows menu and place these at the right side where you can see them. You can add tags there or from the Presets menu. You add the Bing imagery from the Imagery menu and you will see all the layers you have loaded in the box at the right.