Even if you do not have an account, you are still able to search through the public campaigns (though the search is quite basic). Simply visit landing page and click on “Public campaigns” menu item located at the top or scroll down the page.

Enter the search string of your choice and after you see the search results, you will be presented with summary information of the campaign.

If you have an account – you will get a more sophisticated search option and results.
First of all, you need to be logged in with your credentials. Once you do so, you can click on the second icon on your left-side toolbar.

This will bring up the search page. By default, search results show campaigns that you fit in. 

By switching off the toggle "Show only campaigns where you fit the requirements" you can see all other campaigns presented on the platform. Unfortunately, you can't apply to a campaign that doesn't fit your profile settings. Use the search, find the campaign of your interest, and apply. More details about applying to a campaign are here.