Hello @Jerry and welcome
The easiest way is doing it on a live session:
- Boot a Manjaro Install Disk.
- Open a terminal.
- Type:
manjaro-chroot -a
- Now you should be on the local installation within this terminal.
- Then you get the journal of the previous boot (0 → current):
journalctl --boot -1 --no-pager --no-hostname
This way you can upload it:
journalctl --boot -1 --no-pager --no-hostname | curl -F'file=@-' https://0x0.st
Also have a look at these tutorials, since your are new: