How can I overclock FSB or change settings on EP35-DS3R?

First, you want to go to the Advanced BIOS Features page, and set the following:

Limit CPUID Max. to 3.....................: [Disabled]
No-Execute Memory Protect............: [Enabled]
CPU Enhanced Halt (C1E)................: [Disabled]
C2/C2E State Support....................: [Disabled]
C4/C4E State Support..................: [Disabled]
CPU Thermal Monitor 2(TM2) ...........: [Enabled]
CPU EIST Function.........................: [Disabled]
Virtualization Technology................: [Disabled] Enabled if you use Vmware/Virtual PC

Then, on the MB Intelligent Tweaker (M.I.T.) page, set these:

Robust Graphics Booster___________ [Auto]
CPU Host Clock Control_ [Enabled] (this one allows you to change the CPU/FSB clock...)
PCI Express Frequency (Mhz)_______ [100] << ALWAYS SET TO 100, NOT 'auto', especially for overclocking
C.I.A. 2__________________________ [Disabled]
DRAM Timing Selectable_______ SPD __ [Manual] (this one allows you to change the RAM clocking/latencies...)
Performance Enhance = [Standard]
System Voltage Control____ [Manual]

And, on Integrated Peripherals:

Legacy USB Storage Detect___________________[Disabled] *Note* Must be enabled to flash from USB

If it boots and runs, boot up MemTest86+ (which you can find here):
http://www.memtest.org/#downiso