Most theme questions can be answered by reading the theme documentation. I encourage you to read the documentation if you encounter any questions when using your new theme.
Themes are available from two separate Mojo sites, Mojo Marketplace & Mojo Themes. The answer to some questions may depend on where you purchased from, so please note the distinction when it applies. Also, if you made your theme purchase through your host, then Mojo Marketplace would have been used.
If you purchased from Mojo Marketplace, go to My Account / My Purchases to access your theme files.
If you purchased from Mojo Themes, go to My Account / Buyers / My Downloads to access your theme files.
To upload via the WordPress Theme Uploader, you will need to use the birch-theme.zip file. If you purchased from Mojo Marketplace, this file is available to download direct from your My Purchases area. If you purchased from Mojo Themes, this file is located inside of the "Birch - Theme and Documentation.zip" file. Note: Attempting to use the "Birch - Theme and Documentation" zip file directly will result in a "Missing Style Sheet" error.
In order to install, you must use the birch-theme.zip file. Attempting to use any other file will result in a "Missing Style Sheet" error.
On some computers, particularly on Macs, when the birch-theme.zip file is downloaded, it may automatically open. Just look for the folder titled "birch-theme" and compress/archive/zip it back up.
By default, Birch will display your latest posts on the homepage. To use the homepage as seen in the demo, click the Add New button to create a new page. Name it either Homepage or Home. Then look in the far right column for the Page Attributes section and select Homepage from the Template drop-down menu.
After creating the new page with the Homepage template, go to Settings / Reading (in the left navigation bar). For Front page displays, choose A static page, and for Front page select the newly created Home page from the drop-down menu. Then click Save Changes.
You can add and manage slides for the homepage slider by clicking the Slides link in the left menu. To add a new Slide, click Add New. Slides should be given a Title. Images for the slides should be entered in the Background Image section. The optimum size of the slider image is 1600px width x 800px height. To enter a Background Image, click the Upload button. You can drag and drop your image to the pop-up media uploader or click the Media Library link if you've already added the image to your Media Library. When selecting an image, be sure to include a Link URL. (Note: due to the nature of background images, this won't actually create a link here, but leaving this field blank or set to None can sometimes create issues when uploading an image.) Once your image is selected, click the Use This Image button.
In order to view slides on your site, you'll need to have a page created with the Homepage page template and assign that page on the Settings / Reading page. See the How do I have a homepage like the demo site? answer for more details on creating your homepage. Once the homepage is properly set up, you can go to Slides in the left menu to add/edit/manage your slides.
Slides are displayed with a background-size: cover which means that the entire image will not always be visible at all sizes of browser windows, monitors, devices, etc. For this reason, it is recommended to not have any essential elements of the image too close to the edge.
In order to view the featured pages on the homepage of your site, you'll need to have a page created with the Homepage page template and assign that page on the Settings / Reading page. See the How do I have a homepage like the demo site? answer for more details on creating your homepage. Once the homepage is properly set up, you can go to Appearance / Theme Options / Homepage to assign your Featured Pages.
For additional information, be sure to check out the theme documentation: