Forgot my admin password for Ubuntu.

Can you assist me into how to reset my ubuntu password. Was trying to download Adobe Flash update and required my password. I had not used Ubuntu for over a year and did not remember what I had used as administrator. Personally I thought I had deliberately left PW blank as I am the only user of my laptop. Looks like I must have added one... Can you help me reset the PW or find solution to this ? Thanks for all you do! Dave