It is definitely possible to install SRA toolkit correctly. The download page is here and installation instructions are here. It boils down to: 1) downloading correct binaries; 2) unpacking the archive; 3) adding archive's bin directory to $PATH variable.
Alternatively, after unpacking the archive the contents of the bin directory can be moved to another directory that is already part of $PATH for your account. Type echo $PATH to find out what directories are already included. A partial list of my $PATH directories looks like this:
You could move the binaries to any of the directories separated by colons, but not all of them are meant for random programs. For example, from the SRA toolkit's bin directory you could issue this command:
sudo mv * /usr/local/bin
After that you may need to log in and out or open a new terminal window, and typing which fastq-dump should output something like /usr/local/bin/fastq-dump. From that point on it is a matter of reading about program's options and downloading the files as interleaved.