I have opened windows in safe mode , as directed but i don't know what to do next

As you are using a local account, may be you don’t have administrative rights on the local account. So every time you try to install applications or games it prompts to enter the user name and password. It is because user account control has been turned on by the administrators account.

So in this scenario I would suggest you to check the account type of your local account that you are using now. Is it a standard or administrator account?

To check the account type,

Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings.
(If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.)
Tap or click Accounts.

Also try to disable User Account Control. Please perform the following steps.

1. Click Start, and then click Control Panel.
2. In Control Panel, click User Accounts.
3. In the User Accounts window, click User Accounts.
4. In the User Accounts tasks window, click Turn User Account Control on or off.
5. If UAC is currently configured in Admin Approval Mode, the User Account Control message appears. Click Continue.
6. Clear the Use User Account Control (UAC) to help protect your computer check box, and then click OK.
7. Click Restart Now to apply the change right away, or click Restart Later, and then close the User Accounts tasks window