is there w way to scale your assests from 16x16 to 48x48?
Viewing post in Free Pixel Art Tileset - Summer Forest comments
You can do that in any image editor. Resize/resample to 300%. Just choose "nearest neighbor" or "none" for the interpolation method or it'll be blurry.
If you need this to fit into RPG Maker, you may need to cut the sheet into smaller pieces, depending on your need.
This is all very basic image editing available everything from MS Paint to Photoshop, and important skills to have if you want to make a game. Maybe Google "how to prepare custom tilesets for RPG Maker" or something like that.