It is possible to upload several kinds of file to Second Life, to create your own items. To upload files, go to the top menu, Build → Upload, and select the type. A file selector window will open; use it to navigate your file system to locate the file(s) to upload ¹⁾.

The following upload file types are available:

• Image: Uploads an image to be used in SL as a texture. Once you have chosen it, the image preview window opens.
• Sound: Uploads a sound clip in WAV format. The clip must be no longer than 10sec in duration. Once you have selected the clip, the sound preview window opens.
• Animation: Uploads an animation, in standard BVH format. Once the file has been selected, the animation preview window opens.
• Mesh Model: Not currently supported in Firestorm.

There are two more items in this menu:

• Bulk: Allows for bulk upload of images (only).
• Set Default Upload Permissions: Allows you to specify what permissions to apply to newly uploaded files; see here for more on this.

Note that in most cases, you will be charged 10L per file uploaded, by SL. This is debited to your SL account. Therefore you must have at least that much on your account to be able to upload.