1. Use larger needles. Choosing needles that are larger than the recommended needle size will resulting in a larger overall fabric and garment. For example, if the pattern calls for 4mm needles, try using 4.5mm or even 5mm needles.
2. Use thicker yarn. Using a heavier yarn will also make your fabric and garment larger. When choosing yarn for a pattern, look for a weight that is one step above the recommended yarn weight. For example, if the pattern calls for DK weight yarn, try using worsted weight yarn.
3. Cast on more stitches. Adding extra stitches to your cast-on will widen the fabric and garment. The number of stitches you add will depend on how much bigger you want the garment to be. As a general rule, adding 10-20% more stitches should be sufficient.
You can also use combinations of these methods to achieve the desired size for your knitting project. For example, you could use larger needles with thicker yarn, or use larger needles with the recommended yarn weight and cast on more stitches.
Remember that changing the size of a knitting pattern will affect the amount of yarn you need. So, when making changes, be sure to purchase enough yarn to complete your project.