^^ That's hard to answer without knowing what you want the shape to look like after everything is connected.
But in any case the loop tools addon is a really fast way to quickly bridge edges with geometry, if that's what you are looking for:
In the small window in the bottom left corner you can set how many segments you want to add and how flat or curved the new geometry shall be.
The loop tools addon is already included in Blender, you just have to enable it.
See the start of this
youtube video how to enable the addon.