Healthy Nutrition: https://grokker.com/cooking/collection/healthy-nutrition/603ad327b356ab7d31b48ff0 Best wishes! :)

Nutrition is key! As mentioned below you want to make sure you have an app or something in order to track the amount of calories and macros you are taking in. You want to make sure you're getting enough protein in for the day depending on your activity. Protein shakes, collagen, protein yogurts or cottage cheese, etc.

knowing what you metabolize and how many calories you're taking in will really help with gaining mass. If you're vegetarian, you're more than likely taking in low calories. You'll want to ensure you're eating calorie dense foods. The amount of carbohydrates you're taking in will do the rest of the work. Make sure you're getting in enough protein (spirunlina is prob best non-meat option). Ensure you're lifting properly and not doing too much cardio to adversely impact your results.

Welcome, and congratulations on all the healthy exercise!
(1) Here is a collection of videos about healthy nutrition: https://grokker.com/cooking/collection/healthy-nutrition/603ad327b356ab7d31b48ff0
(2) Here is a sign-up page for an upcoming live q&a webinar next week with a professional nutritionist, Dr. Chris Mohr: https://us02web.zoom.us/webinar/register/1916777799414/WN_c84AwwbSSe2FD9tPlwe-8Q#/
(3) Here is where you will be able to find the replay video of Dr. Mohr's webinar sometime after it airs next week: https://grokker.com/cooking/expert/chris-mohr/59668b0b4ec7aa0af8f01ecb/videos
(4) Here is a collection of fitness videos that you might enjoy, including CrossFit videos: https://grokker.com/fitness/collection/running-football-crossfit-barbells-mud-runs-warm/6009d3963fa6704a3439d0ef
Good luck and best wishes!