It looks like what you need is a little help on how to install the Sun JRE on Fedora 7. Here's something I know works. This is the way to download the JRE and extract it and set it up so that FrostWire picks it up. I have done this for a friend a few days ago (not for the 1st time though), so I know it works.
Don't get put off by the descriptive answer, I'm going to submit it to Linux Answers section. That's why it seems so long
(If you don't have sudo configured you'll have to either use 'su' or login as root to use the commands I have provided with 'sudo' at the beginning)
1. First download the JRE from Sun. http://java.sun.com/javase/downloads/index.jsp
JRE 6 Update 2 is the latest stable release as of this writing. You can get the Linux self extracting file (.bin) or the RPM archive (-rpm.bin) file.
2. After you complete your download, go to the directory you have it on disk. Eg: $ cd ~/gundumfx/Desktop/ if you have it on your desktop
3. Change the permissions so that you can execute the file
Eg: $ chmod a+x ./jre-6u2-linux-i586.bin
4. Execute it Eg: $ ./jre-6u2-linux-i586.bin
5. You'll have to go through the Sun's license notice and accept it to use the JRE. After this the package will extract and you will have a directory Eg: jre1.6.0_02 if you downloaded the .bin file or you'll have a .rpm file if you downloaded the -rpm.bin file.
6. If you now have a .rpm file, you only have to enter the command
$ sudo rpm -Uvh jre-6u2-linux-i586.rpm
You are done. Contratz!
But if you downloaded the .bin in the first place, please proceed from step 7.
7. Move your new JRE directory where people can access
Eg: $ sudo mv ./jre1.6.0_02 /opt/
8. Add the path to the bin directory within your JRE directory, to your PATH. Use your preferred editor to edit the relevant configuration file to set the PATH. If you are going to add it to system wide PATH so anyone can get it, use /etc/bashrc. If you just want it for you edit your .bashrc (~/.bashrc)
Eg: $ sudo vi /etc/bashrc
9. Add the following lines after everything (replace /opt/jre1.6.0_02/bin with your JRE bin path)
save (write to) the file and exit. Now, next time you log in, you'll have a Sun JRE ready for you. Congratz!
FrostWire will detect your new JRE and use it.