Like Roy Kelley mentioned, use Google.

Enter in Google like so:

site:activerain.com/questions "your term"

e.g., if you are looking for questions about CRMs, use site:activerain.com/questions "crm"

Or, if you want to be more specific:
site:activerain.com/questions intitle:"crm"

This will look for questions that have CRM in the title of the question.

Use Google for the best results.

You've gotten good answers from Roy Kelley and Barbara Todaro for two different kinds of searching.

put the topic in the search box at the top of every page next to the word "activerain"... click on the arrow and voila....

Barbara Todaro and Roy Kelley have you covered.  Good luck to you.

I usually just put the search topic in the search box.

I'd recommend starting at the search box to the right of the AR logo at the top.

With Roy Kelley and Barbara Todaro arriving before me, nothing I can add!

I've always just put the topic in the AR search box. It's not perfect but it's always worked good enough for me Kim Richardson 

Kim,

Excellent answers from the group  All the best to you.  A

Search box on the upper left AR header. Works good or do it like Ryan Huggins said.

I would bookmark this article from Lifehacker:

20 Google Search Tips to Use Google More Efficiently

Here is my blog on how to search the Q&A section.  Works for other websites too.

https://activerain.com/blogsview/4925743/how-to--search-the-q-a-section

Looks like I was late for this party.  Seems you already got your answer.

Dario Ferreira nailed this one!  

Yes, great answers you got.

I think you can only search by the pull-down topics.

Excellent answers from the AR family of experts. 

It appears you may already have your answer. Good luck!

Put the topic you are searching in the Search Box & press enter. 

The only way you can search a specific question is by a search box in an upper left corner. Unfortunately, you can not filter by date, location, or any other specific criteria.

Looks like Dario has a good technique, Ryan posted a blog on this a while ago too.