How can I get a quarter out of my dead grandmother's house?

You have to give us much more information. Is there a Will or Trust, who are the heirs, has probate been filed or does anyone intend to do so, who is the executor, etc. If you are an heir under California law, you will have to probate the estate so a transfer of title to the house can occur. See the Nolo Press books on Wills and Probate to get an idea of the process.

We need more facts. Will? Trust? Neither? How does title stand? Family structure? If you are not on the title, you should have a free conference with a lawyer specializing in trusts and estates. Probate (a complicated court proceeding) may be necessary.