Please use the following template:
Problem: So I'm new or relatively new to the hacking scene.... and I was wondering what type of attacks are used for when you have access to a user/computer on a network, what kind of attacks you can do to gain access to other computers on the network
If you do have physical access to a machine, there is a known (and i think still unpatched) vulnerability with some versions of Windows. If it is a Windows 7, 8 machine it is really simple, you just need to have a windows disk, boot it up and use command prompt to make a few changes.
Take a look at this for more detailed info:
http://www.howtogeek.com/96630/how-to-reset-your-forgotten-windows-password-the-easy-way/If you just have have access to the network, I would recommend the same as already stated above, first thing I would do is to run Nmap on the network.
Nmap should give you some IP addresses with juicy info about them, like current OS, possible vulnebs, open ports etc. With that in hand you can start searching more information about what you have found.