Directly searching for relevant classifications is tricky. You may find initial relevant Cooperative Patent Classification using the USPTO website’s Site Search box, using your identified keywords. In the Site search box found in the top right hand corner of the home page enter “CPC Scheme [plus keywords(s) describing invention]”; for example, if you were trying to find CPC Classifications for patents related to umbrellas, you would enter “CPC Scheme umbrella”. Scan the resulting classification’s Class Scheme (class schedules) to determine the most relevant classification to your invention. One more effective option is to use keywords to initially find some related patents and pick the classification codes from there.