If you are waiting on a UC appeals decision, they recommend you submit your SIR and $100 to the UC you have an offer from and had planned to attend--while waiting for the appeals decision. Appeals decisions are not guaranteed, and you don't want to loose a spot in an already guaranteed offer. If anything, you will loose your $100 deposit which is better than NOT getting into a UC at all.
To locate your portal, click on your UC:
UCB: http://students.berkeley.edu/myberkeley/home.asp
UCD: https://sisweb.ucdavis.edu/owa_service/owa/bwzkugap.P_AccountSetup
UCI: https://www.admissions.uci.edu:8443/cgi-bin/maa_uci.cgi
UCLA: http://www.admissions.ucla.edu/newbruins/myucla.htm
UCSB: https://www.admissions.ucsb.edu/admitted/stepstoenrollment.asp?subsection=5
UCSC: https://my.ucsc.edu/psp/ep9prd/?cmd=login&languageCd=ENG
UCSD: https://a4.ucsd.edu/tritON/Authn/UCSD?shire=https%3A%2F%2Fact.ucsd.edu%2FShibboleth.sso%2FSAML%2FPOST&time=1335650993&target=https%3A%2F%2Fact.ucsd.edu%2Fjlinkauth%2Fapplicant%2Fstudent%3Ftarget%3DL3N0dWRlbnRBcHBsaWNhbnRzL2FwcGxpY2FudHRyYWNraW5n&providerId=https%3A%2F%2Fact.ucsd.edu%2Fshibboleth-sp
UCR: http://vcsaweb.ucr.edu/MyUCR/
UCM: https://my.ucmerced.edu/uPortal/render.userLayoutRootNode.uP
