That looks very nice indeed!

High action at the 1st fret means that the nut string slots aren't cut deep enough.

You have the options of:

1) Removing the nut, filing the bottom down a bit, put it back (without glueing), string up again to tension, then see how it feels. Repeat until it's low enough to play properly. If you file too much off, either stick a piece of veneer under the nut, or buty another nut and repeat the process.

2) Buying some nut files and cut the slots to the right depth yourself. Worthwhile if you plan on making several more guitars, but a good set will cost you around AUD$200 or more.

3) Take it to a luthier to set up. A decent one will do it without any questions. A poor one will say they don't work on kit guitars (it does happen).

You may well also need to adjust the truss rod and maybe even level the frets to get a really good action. It's all fairly easy stuff, but fret levelling again requires purchasing some appropriate specialist tools. Cost-effective and satisfying if you plan to make more guitars, but for a single guitar finding a luthier is a better option. Or there may be a forum member with the skills and kit fairly near you (where are you?), whom I'm sure would be glad to help.