Note that manual installation of Biblatex and Biber is not recommended except in exceptional circumstances.
Such circumstances include:
you've been bitten by a bug which is fixed in a newer version, you need the fix urgently and you will remember to undo the manual installation at the appropriate time (and you'll recognise when that is);
you have been foolish enough to update your TeX distribution right before a deadline, have no roll-back plan and the update has broken your bibliography, you plan to fix the real problem after the deadline and will remember to undo the manual installation at that time.
In all other cases, the best course is to update your document or other packages to use the new Biblatex/Biber or to wait for the fixed version to be available through your normal update routine.
Note that there is no guarantee that rolling back Biblatex/Biber will work with an updated TeX distribution, although it is likely in most cases to work in the short term.
Caveat emptor ...
If you are sure you want to do this, then proceed as follows. These instructions assume you are using TeX Live on a Unix-ish system (Mac OS X, BSD, GNU/Linux etc.).
You need to download matching versions of Biber and Biblatex from SourceForge: Biber and Biblatex.
At the command line (e.g. Terminal for OS X users), navigate to the directory you downloaded the files to.
ls *.tgz *.gz
should show you a file named
biblatex-<version>.tds.tgz and another named
<version> is the version you need of Biblatex and
<arch> matches the architecture of your OS.
mv biblatex-<version>.tds.tgz $(kpsewhich -var TEXMFHOME)
pushd $(kpsewhich -var TEXMFHOME)
tar -xzf biblatex-<version>.tds.tgz
The last command should return a file in you personal TEXMF tree and not in the main TEXMF tree. It should be somewhere in your home directory.
mkdir -p ~/bin
tar -xzf biber-<arch>.tar.gz
This should produce a
biber binary, possibly in a sub-directory.
mv <sub-directory>/biber ~/bin/
To use your downloaded copy of Biber, use
~/bin/biber <filename> rather than
biber <filename>, to make sure you get the correct one. (You could adjust your
PATH to automate this, but it is not worth it for a very short-term temporary workaround.)