You level up by earning XP through activities like harvesting, collecting from Gear and Animals, making Recipes, claiming Ribbons rewards, and more. Once you reach a certain XP threshold, you level up.
Your XP Star/Bar is located at the top-right corner of your game screen. To see how much XP you need to reach the next level, hover over it.
You can customize the XP Star so that the Bar always shows. Just open your Settings → Page 6 and make sure the option Classic XP Bar is checked.
The Progress tab shows what rewards await you when you reach the next level and what items you will unlock.
Each time you level up, you’ll receive 1 to 4 Ranch Cash (based on your level) and some Coins. Your Fuel, Power, and Energy will also be fully refilled.