Create an account.
Go to the Create account page
and fill out the form.
You will receive an email containing
your account ID (a long random string).
Save this email.
Download and install BOINC.
Go to the download page,
download the BOINC software for your type of computer,
install it, and run it.
You will be asked to enter the project URL
(http://boinc.berkeley.edu/) and your account ID.
That's it!
How it works
When you run BOINC on your PC,
it works as follows (see below):
Your PC gets a list of instructions from the project's
scheduling server.
The instructions depend on your PC: for example,
the server won't give it work that requires more RAM than you have.
The instructions may include many separate pieces of work.
Projects can support several applications,
and the server may send you work from any of them.
Your PC downloads executable and input files
from the project's data server.
If the project releases new versions of its applications,
the executable files are downloaded automatically to your PC.
Your PC runs the application programs, producing output files.
Your PC uploads the output files to the data server.
Your PC reports the completed results to the scheduling server,
and gets instructions for more work.
This cycle is repeated indefinitely.
BOINC does this all automatically;
you don't have to do anything.
Credit
The project's server keeps track of how much work
each participant has contributed;
this is called credit.
The following system is used
to ensure that credit is granted fairly:
Each work unit is sent to at least two computers.
When a computer reports a result,
it claims a certain amount of credit,
based on how much CPU time was used.
When at least two results have been returned,
the server compares them.
If the results agree, then users are granted
the smaller of the claimed credits.
There may be a delay of several days between
when your computer reports a result
and when it is granted credit for the result.
Your User page shows you how much credit is 'pending'
(claimed but not granted).
More information
More detailed information about participating in BOINC projects
is here.