On the "Send Ether & Tokens" page on MEW, click View Balance Only (Must use one of above options to send) and paste your address.
In a new tab, go to Ethplorer.io
Type in the name of the token into their search bar, or navigate to your address and click on the token's name from that page.
At the very top on this page page is the address.
Below that there is a field called "decimals", which is a number between 0 and 18.
Back on MEW, click the Add Custom Token button on the right sidebar.
Paste the Address from the top of the Ethplorer.io page
Type in what you want to call it - the name or the symbol.
Paste the Decimals from Ethplorer.io.
Click "Save".
You can now send your new token and see it's balance in the sidebar!