Can't log on with admin

I just got a new computer and I don’t know if that is the reason but I used to be able to type “admin” for my login user and then my password and it would take me to my blog/website dashboard so I can make changes to my site but now I can’t. This is the first time I have tried on my new computer and it isn’t working. Any help is greatly appreciated. I have no clue what I am doing. When I set up my website 2 years ago it was just luck that I was able to do it and follow directions so easy-to-understand instructions are needed here. Thanks.