Congratulations on your new manjaro computer. At the first start-up you will have to set the language and keyboard layout and create a username and password.
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Choose your language and click on next

Choose country and region and click next

Choose keyboard layout, for example qwerty inter., than click next

Enter your name, your username (may / may be the same, but not starting with a capital letter)

Enter a password twice.

Check to log in without entering a password, or if not checked your password will be requested every time the PC is started.

Be sure to tick yes in the checkbox to use the same password for the administrator account, so you will be able to update or install software.

Or you can optionally enter a different password for the administrator account or use the same password of the created user. Click next

View the entered data, if something needs to be changed, click on the "back" button

If everything is ok, press the "install" button

The system will now set everything. Then tick restart and click on complete. The system will restart, after which manjaro is ready for use.