I’ll try to help…
There is a PATH variable in all unix systems. This variable holds a bunch of directories. If you type a command, your OS will search for this command in the directories given by PATH.
To see what’s in PATH:
Then there was the question where to install your java. I’d suggest to create a folder called java-[yourversion] in /opt. (see this link that describes opt).
In the extracted java-folder there probably is a folder called bin (for binaries). If you find the java binary in there then you have to add it to the PATH variable:
The binaries have to be executable, check with
ls -l. If they are not executable (look for an x in rwxrwxrwx) you can make them executable with the command
chmod +x [yourbinary]
After all this answer assumes you have downloaded the correct binary for ARM.