This presumes that the part of the wiki ("space") the page is to be added to exists, if it doesn't, see Creating a space below.
Navigate to the space or page where you want the new page.
Click the New Page hyperlink top right. The default page's name is by default _New Page_. you will want to change this. Add some content and click Save.
The new page opens.
Note that putting a link (see below) to a non-existent page creates it.
Once the page is created, you can type text in it or use copy text from Word to Confluence. Some Word formatting will be retained.
Attaching a file to a page in the wiki
Click the Insert/Edit Link icon (it looks like a chain) on the toolbar.
To link to a page in the UCL Wiki, search e.g. Global Spaces for the page. Click the link and click OK. (Attachments are included in the search.)
To link to a page on the Internet, click on the *External Link* tab and enter the address. (it may be safest to copy the address from your browser's Address field).