How to overclock i5 2310@2.90Ghz??

Your CPU is locked, so you can't overclock. You can try to raise the motherboard's BCLK. Enter BIOS and see if it's possible. More likely than not, you can't, but it's worth a try.
If you can, rais it by 10MHz increments, and run the Prime95 stress test for about 1/2 hour. If it remains stable, then crank it up another notch. Repeat this until your system is unstable. When it it, then drop it down a few notches. Run Prime 95 for about 6 hours. If it runs good, then you have an overclock.

Word of Warning: raising the motherboard's BCLK also affects the RAM and GPU. I am not liable for any damage you cause by overclocking.