I have a website at modospot.com , does anyone know how i can access the main website and its subdomains? I only know how to access its subpages. Its a cpanel type.

I assume that you are the authorized owner/administration of your domain name: modospot.com and the authorized website administration of your cPanel with your own cPanel username and cPanel password, sometimes called FTP account (FTP username/password the same as cPanel account). Also you are either beginner or experienced webmaster to modify your own template-based website using HTML scripting (coding).

If you are familiar with scripting HTML to be modified your template-based website at modospot.com, then you can access using "FILE MANAGER". The file manager enables you to upload, modify, move, copy, create and delete files and folders through a web browser much the same as you can via FTP software.

If you want to add subdomain to your website: modospot.com, this subdomain enables you to create sub domains on your account. For example http://subdomain.yourdomain.com This can be useful if your company has different departments which you want to brand individually.

Creating a New Sub Domain

Simply enter the name of the sub domain you wish to create, check the correct domain is selected in the drop-down menu and click the Add button.

Setting Up Re-Direction

You can have a sub domain automatically re-direct the visitor to any other domain you specify using this option.

Simply select the sub domain you wish to add re-direction too and click the Setup Redirection button. Enter the URL of the site you wish to re-direct to and click the Save button.

For example http://yourbusinessowner_company.yourdomain.com., This subdomain is also useful if your potential business owner cannot afford buying domain name and hosting server which you can add your business owner's company to your account to be branded individually. Great for your family and friend who want their own website individually, for example http://yourbrother.yourdomain.com, http://yoursister.yourdomain.com, or http://yourfriend.yourdomain.com, goes on.

====== My Comment from my experience =======
That is where you come in making money to market your target audience who need web designer creating their website but not able to afford buying domain names/hosting service. Your target audience hires you and pay your subdomain account accessing their own FTP account under your cPanel account.
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Source Site of cPanel tutorial guide: http://www.cpanelguide.net/. This is unoffical guide site.  Just click on a menu item to see the associated article. When you finish read the article, return to cPanel main menu, just click the button of "house" icon.