Turbo Mode should be enabled by default. The BIOS controls this; use BIOS Setup to change - if it supports this being changed.
For more information (get ready to do a lot of reading; this isn't a simple thing), consult these sources:
- What is Intel Turbo Boost Technology and How Does it Work?
- Why Am I Not Getting the Intel Turbo Boost Frequency?
- My Intel Core Processor Does Not Reach the Maximum Turbo Boost Frequency
- Frequently Asked Questions for Intel Turbo Boost Technology
- Frequently Asked Questions About Temperature for Intel Processors
Hope this helps,