You are in your Dashboard "Add New Page."
Did you download TinyMCE from WordPress? And save it to your Desktop or someplace on your computer where you can find it?
Then did you go to Plugins in your WordPress Dashboard and click "Add New"?
Once you were there, in "Install Plugins" did you click on "Upload" in blue at the top?
Then did you click on the "Browse" button? Which takes you to your computer files. And then click on TinyMCE where you saved it on your computer? And hit a blue button on your computer that says "select" or something like that.
If you did all that, then you can continue with my other instructions about going to "Settings" on your WordPress Dashboard, click on TinyMCE, which should be there in the sub menus now. This takes you to Editor Settings. In Editor Settings, drag the TinyMCE icon buttons you want into the (blank) toolbar space above. Make sure to check the "Load CSS" box. Return to your New Page, and toggle the toolbar, last icon button on the end, top row. The TinyMCE toolbar you just created should drop down if it is not there already.