Hi@ThasinAbir,

Thank you for contacting our community.

Could I confirm what is the model of your router? Archer A10 or Archer C50?

For most new Archer Router models, you were asked to set an admin/local/login password when you accessed the web management interface for the first time.
For a few older Archer Router models, the default username and password are both "admin".
If you want to change the admin/local password, please log in to the web management interface of the TP-Link router by referring to this link: How do I log into the web-based Utility (Management Page) of TP-Link wireless router? , then please Go to Advanced > System Tools > Administration > Account Management. Enter the old password and the new password. Then click Save.

Best Regards.

Hi @Sannyahmed8090,

Thank you for contacting our community.

May I know what the model number of your device is? Please refer to How to find the model number of your TP-Link device 

There are two methods to check and customize wireless settings of your Router: 
Through the web management page, please refer to How to Change your Security Settings on your TP-Link Router
Through the Tether APP, please refer to How to change wireless settings of TP-Link wireless router on Tether APP

Best Regards.