How do I reset my password if I can't log into my macbook?

Read through to the end if you have to

Change or reset the password of an OS X user account - Apple Support

Boot into recovery mode holding Command + R at startup. Select Utilities from the menu bar then Terminal. In Terminal type in resetpassword then return. Select the startup disk, user account, then enter the new password. When finished click Save then restart.

After resetting the password you need to reset keychain.

If your Mac keeps asking for the login keychain password - Apple Support

If the password field is not accepting any input then the password itself isn't the issue.

Is the keyboard working everywhere else?

Keyboard Doesn’t Work

Keyboard Keys Do Not Respond

sandrafromtarpon springs wrote:

I have tried going through the Terminal and I couldn't type anything in the field. I think I'm having a keyboard issue. I connected an external keyboard and I was able to type after that. Any suggestions about fixing my keyboard?

Thanks

Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379

Try a restart.

Do a backup, using either Time Machine or a cloning program, to ensure files/data can be recovered. Two backups are better than one.

Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later.

Isolating an issue by using another user account

If the problem is still there, try booting into the Safe Mode using your normal account. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer. For each disable/delete, you will need to restart if you don't do them all at once.

Safe Mode - About

Safe Mode - Yosemite

Take it in for a repair. Use https://locate.apple.com/country to find a store or service provider.

Yes, it is 2 more tests to see if it work at all. If it won't work in a new account or the Safe Mode, then use chroot's answer.