tony_rules

Yes you need 64-bit java for it. Also for installing mods, they go into the mods folder for the modpack. Clicking the cog icon under the modpack logo on the launcher should give you a button that says "Open Folder" or what have ya, the mods folder is there.
 
As for the java, when you install 64bit, uninstall all previous versions before hand and reboot to ensure the installation goes smoothly, also run it in administrative mode so it can do some things it needs (otherwise youll probably end up with a "cannot create java virtual machine" error or a "java is not a recongizable command...etc"

Does it do it every time you play on a new map? Are you playing on the internet?
 
There are a lot of variables.
 
For example you could just be lagging.
 
Your java needs to be updated.
 
Your video card is too "weak" or drivers outdated.
 
You are using a hacked Minecraft client.
 
You didn't install it correctly.
 
You have other programs running in the "background" that cause your RAM to be consumed at a rapid rate.
 
You are using 32 bit java.