Hi @Dhananjay_Patil ,
You can easily use CDNs in your web templates. However if you want to store files within the Portal you can use Web Files (see official docs here). One thing that you might encounter is that you cannot upload js files as attachments. There are two ways to allow this issue:
1. You allow attaching js files as notes. To do so you need to Settings>Administration>System Settings and in General tab remove js from the list of bloked file extensions. Be aware that this will allow any user to attach file with js extension.
2. You can change extension of your js file to something like .es and upload it to the system. This works if you don't change you file frequently.
