Make sure that all parts came in good shape and no apparent damage is done on the way.

Disconnect 2 edge led matrix modules from the screen. Be careful not to bend the pins, otherwise it would be a lot of dancing to put them back later on. Don't worry about orientation, they have markings on one side

Solder headers to the Wemos D1 module. Long part of the header should be directed to the motherboard. Make sure to align them right, use motherboard as an aligning tool.

Start with just one pin each side and double check your work. Then you can proceed to other pins

Now solder screen headers. They will go the opposite side of the motherboard. Again, use screen as aligning tool.

Solder buzzer on the same side where Wemos headers are. Make sure to note polarity.

Mount brass stands to the screen, use 4 bolts first

Then finish the other side. Make sure to connect the screen in the right direction. Check DIN and DOUT pins on the screen and motherboard connected to each other.

Connect power to Wemos' USB port either from laptop or powerbank. At this stage clock will turn on and show "Loading" screen.

When ESP starts for the first time, it will configure AP point named ESPXXXXXX. Connect to it using your phone and you will be redirected to WiFi captive portal, where you can provide WiFi network credentials. After that Clock will connect to known WiFi automatically

All Clocks are shipped with pre-installed firmware. Unfortunately, timezone settings are hardwired in the firmware (one day I will rewrite it to be able to change it without re-flashing). So unless you order from Europe, chances are you need to reconfigure timezone are pretty high.

After you install vscode and Platformio, and hopefully able to build firmware, you just need to chang single line in the platformio.ini file

build_flags =
    ${env.build_flags}
    '-D TIMEZONE="CET-1CEST,M3.5.0,M10.5.0/3"'

Tricky part is to know the right value to replace. tz.h file will give you more than 200 common examples

//*********************************************************************************************************
//    Examples for time zones                                                                             *
//*********************************************************************************************************
//    UTC                       GMT0
//    Africa/Abidjan            GMT0
//    Africa/Accra              GMT0
//    Africa/Addis_Ababa        EAT-3
//    Africa/Algiers            CET-1
//    Africa/Blantyre, Harare   CAT-2
...
//    US/Michigan               EST5EDT,M3.2.0,M11.1.0
//    US/Samoa                  SST11
//    US/Los Angeles            PST8PDT,M3.2.0,M11.1.0
//    US/Houston                CST6CDT,M3.2.0,M11.1.0

and this website will give few more on top of that.

When the right value is found, rebuilding and flashing firmware will finish the quest.