A) open SSH to your server, if SSH will not connect due to disk space full in tmp, reboot your server in cloud server manager then try again.
Once connected run the following command
once tmpwatch is installed run command
/usr/sbin/tmpwatch -am 12 /tmp
this will delete all files over 12 hours old
next, we will configure your server to do this automatically.
from SSH type:
go to the very bottom and paste
0 4 * * * /usr/sbin/tmpwatch -am 12 /tmp
then press Control+X (on PC) or Command+x (on Mac) you will get confirmation do you want to save. Type Y for yes, and press enter