My Mac is locking up and running slow

[dewdropin]

I'm a new user to iMac, my kids use it for school and games. Lately it's been locking up and running slow, then takes off to catch up. I'm use to a PC and know how to clear out the registry and some other stuff, but when it come to the mac I'm lost. Need help!!😕

 

[maclover001]

Open up Activity Monitor (Macintosh HD > Applications > Utilities), and post a screenshot during one of its slow moments.