I saw somebody in World of Minecraft:Realms with a HD texture pack (as well as /chat) and i would like to know how to install texture packs to my Realm, not just for me, but so when somebody comes to my realm they see the TP as well, I tried going on womrealms.com and using my control panel to upload a terrain.png of Misa's 64x texture pack (for Beta) but after uploading it brings me to a page that says 413 Request Entity Too Large

Please help me :(