Using VMware may slow down your system. I installed VMware in my laptop running Windows 7 which reduced performance a lot. As you have Ubuntu OS installed in your computer, you can use it directly instead of using in VMware. Running Ubuntu in VMware will consume some time and it will lead to loss in your productivity. Assuming that your computer has good hardware configuration (8GB RAM), I have given the steps to install Ubuntu in VMware Player.
1. For installing Ubuntu in VMware Player, ISO file(OS)is required. It can be downloaded from Ubuntu official site.
2. In VMware player, in its homepage there will be option called "Create a New Virtual Machine."
3. It will ask for ISO file, locate the ISO file. ISO file be will be present where you have downloaded. After the ISO file is selected, click next to continue.
4. It will prompt for Username and Password. They are mandatory.
5. Give a name for your new virtual machine. It will ask you the location to save it. Give the location and save.
6. This step is important. Here you need to choose the storage size and RAM. It is better to keep it default. Providing extra storage or RAM will terribly reduce your computer performance.
7. Its all over now. Click finish, VMplayer will start installing Ubuntu OS.