Gear shifting is hard, do I need more clutch fluid

It's difficult to say what the problem could be without more info. Does your civic have an automatic transmission? If it does and you are having difficulty shifting or it doesn't shift smoothly there are lots of possible causes inside the transmission and there may be little you can do on your own. Checking the transmission fluid level and adding more can be tricky because you must pay attention to the fluid temperature. Most transmission dip sticks have level marks for both cold and hot fluid. Overfilling the transmission fluid can potentially damage your transmission. If your transmission is having serious problems the fluid on the dip stick will usually have a bad burt smell. In any case automatic transmission problems can be really difficult for a beginner mechanic to do anything about. If the fluid is smelly I suggest talking to a mechanic, preferably one who has lots of transmission experience.

If your car is a manual... well... topping up the transmission oil is less risky if you pay attention to the dip stick level, but if you are having trouble shifting it is either a problem with your manual clutch being out of adjustment or worse the bits inside the transmission are getting badly worn.

Hope this helps. Good luck.