How to set password to my TP-Link router and control the password time to time?

Generally, you enter the configuration of the router by using your browser and entering the router's IP address. Usually 192.168.1.1.

Then it depends on what password you are referring to. There is usually a password to get into the configuration and there may be a password to connect to the router wirelessly. Where that is depends on your specific model. You should have either a manual or PDF file with instructions on where to do this. If you don't you can download one from the manufacturer's website.