For a quick install, just follow these steps:

tar -xzvf qjoypad-4.?.tgz
cd qjoypad-4.?/src
./config
make
make install

If those steps don't work for you, here are some common problems:

Compilations fails with along the lines of:
axis.h:21: error: expected class-name before ‘{’ token
axis.h:22: error: ISO C++ forbids declaration of ‘Q_OBJECT’ with no type
axis.h:24: error: expected ‘;’ before ‘friend’
axis.h:29: error: ‘QTextStream’ has not been declared
axis.h:31: error: ‘QTextStream’ has not been declared
axis.h:40: error: ‘QString’ does not name a type
axis.h:44: error: ‘QString’ does not name a type
axis.h:89: error: ISO C++ forbids declaration of ‘QTimer’ with no type

Most likely you're using the Qt3 version of qmake; QJoyPad needs to use Qt4 to 
work properly.  The config script is supposed to detect this properly, but in
the event it fails you should find what the proper executable is (if you think
you've found it run it with the --version option to make sure it is for Qt
4.0 or greater).  Then rerun the config script with the --qmake4bin=BIN option,
where BIN is the executable name of the proper qmake binary, or a path to the
proper qmake binary.