First of all, download and extract mypaint 1.0.0:
wget http://download.gna.org/mypaint/mypaint-1.0.0.tar.bz2
tar -xvf mypaint-1.0.0.tar.bz2
cd mypaint-1.0.0
Now, if you take a look at the readme file
cat README
you'll see that it needs scons to compile. If you haven't installed scons don't panic, there is an easy to get SlackBuild:
