Simply log in with any username and password.
This is just decoration, the game is offline.
Select the 'Timeline' option at the top, and then find the month/year that you want on the calendar. Click the specific day on the calendar that you want to jump to (you can only select days on which there was a new update).
Your Windows defender is likely removing the game. You will have to disable it or allow the game to be in your PC.
You must make sure you installed the clothing package. Open Options > Settings and install the clothing.
Run the app as an administrator.
All your penguins are stored in your save data. The easiest way to find this folder is opening the mods folder (open Options > Open mods > click on "Open Mods Folder"), and then next to the mods folder, you can find the data folder.
You will need to setup a LAN environment. There are two main programs you can use: RAdmin VPN (Windows only) and ZeroTier. Once you have setup the LAN environment (the process depends on the program), the host must go on the menu and click on "Change your server's IP" and copy and paste their own IP (The IP inside the VPN, not their real IP!). Note that this is done WITHOUT the port (:24105), only the IP. Then for the others to join they must go on "Change the client IP" and paste the same IP used by the host.
WARNING: Make sure only to invite friends. The server is full of vulnerabilities for hackers!