If completion tracking is turned on for the site and the course, you should have a couple things in your course that should help. If you don't, there may be permissions issues, so we'll start there.
First...do you have site permissions or course permissions or both? This matters because if you have an inherited role but don't have explicit Teacher role in a course, some of the options don't show up. If you have an inherited role, to resolve this in Administration, look for the Switch role to and choose Teacher (or equivalent--mine is actually called Facilitator) OR just give yourself an explicit Teacher role in the course.
Second...Course completion tracking should add an option in your Course Administration block that says Course completion. This is where you tell the course what must be completed to receive credit for the course--could be quiz, forum, etc or some combination; could be a course grade (I don't ever use course grade because it has caused me some trouble...).
If you see Course completion but no activities are available, you'll need to set activity completion in the relevant activities & resources--to do this edit the activity and the last section on the form should be Activity Completion--there are generally 3 options: Do not report completion, Students can manually mark the activity as complete or Show activity as complete when conditions are met (and you have to check the completion requirements, depending on the activity).
Third...You should have a block called Course Completion Status in your course. This is a stand alone block at may be at the bottom unless you've re-positioned it. It will show one of four messages, depending on course conditions: Course completion is not enabled (tracking isn't turned on in the course settings), No completion criteria set (tracking is on but you have not set completion criteria), You are currently not being tracked by completion in this course (completion criteria is set but you are not a student, therefore will not show up on the list--if you are the teacher, this is normal and correct) and a message that provides status (this indicates where you are in courses you are a student in). If you are a student and a teacher (this happens for me a lot--government training requires the teacher to also complete the training), you'll have a link in the last two that links you to all reports, only a student gets just a link to their own stuff.
Fourth...reports. In Course Administration->Reports, there are Activity reports and Activity completion reports. You would not be able to run them by specific month but you could run them for always, download them to csv and then turn on filters and filter by date range in your spreadsheet software. This is what I do a lot--not for dates, but for other information. Each activity should also have some reporting (Lesson's reporting is pretty rudimentary, but everything else gives pretty decent reports).
I don't know which Certificate module you are using--there is more than one. The one I use (just Certificate) displays the number of issued certificates when you access the activity as a Teacher. If you save the certificates, it will allow you to view a list of these issued certificates.
Whew! I hope this is helpful.
