Follow this guide first to update your ROM to 2.14.401.3 manually:
[GUIDE]How to update HTC Wildfire S/Marvel/A510e/GSM to Software Version 2.3.5

Then go on to update your bootloader starting at step 3 of this guide:
[Guide] How to root the Wildfire S with S-ON (finally!)

 

Unfortunately, this link will not result in a rooted phone. See other posts which point out that S-Off is required for a WFS 2.3.5. Older WFS's were rootable with S-On, but 2.3.5 seems to have stopped that.

Unlocking your phone is relatively easy now that HTC provides the means. But rooting a WFS 2.3.5 is proving impossible. I've not yet tried X-Clip but am thinking it might be the only way.

 

Actually, I think the opposite is true. By far more WFS have been rooted by unlocking the bootloader under 2.3.5 than any other method. Notice the dates on those who have hit the thanks button in the rooting thread. It works!

 

I managed to get my s-off with the goldcard method! Worked wonders for me. This looks like the link i used.... http://forum.shaarpmind.com/showthread.php/236751-Wildfire-S-Safe-free-Unlock-without-any-box

 

This only works with CDMA phones (no sim card) and we already have a thread for this on Androidforums:
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