How do I continue editing

First you need to learn the very basics of working with the application before you go any further. For an excellent introduction to FCP start with Steve Martin’s 60 minute intro https://www.youtube.com/watch?v=HqUP7Zgeuck. For a more in depth introduction use the IzzyVideo tutorials. The version is a bit dated but the principles are the same. 

A project is an FCP7 sequence. It has a clapperboard icon. It’s inside the event at the top. It’s also accessed from the Projects Smart collection that you see at the top left of your screenshot.

Do follow Tom's solid advice. There is a lot to (re)learn, and the best way to get started is by following these great tutorials.

Rest assured that everything you need to do can be done; but the application is quite different, and there is an adaptation period.

If you stick with it, soon it will make sense, and the old ways become... old.

Just a quick note to address your concern about the project: if you click the name of the project, you can choose to Reveal in Browser, and you can also adjust the project properties:

Either way, you can take the opportunity to rename it to something meaningful.

If you grab the front or back end of a shortened clip in the timeline you can drag it out to its full length just as in the original FCP.

If you shorten the front of the first clip in the timeline, it may look as though there is a big gap but really there is not and your video starts at the beginning of the first clip. Look at the timecode circled in the screenshot.

If you don't like the look of the imaginary gap simply drag the clip to the left or press the ⇧ and Z keys to make the timeline fit the window.

I also notice that you have got your clips in the Browser stretched out so that each one takes up several lines. Generally I find it more convenient to have a clip represented by a single "thumbnail" regardless of its length.

The clip (Goodbye JAZZ) arrowed is several minutes long.

To shrink the clips in the Browser, select the filmstrip icon in the red hexagon and drag the slider in the red rectangle all the way to the left.