get yourself on a good routine, one made by professionals, dont make your own. google 5x5 or Starting Strength, those are pretty good. im currently doing my own variation of a 5x5 routine and its working great. next get your nutrition in line. since you're vegetarian, you'll have to read into how to diet for muscle building as a vegetarian to make sure you're hitting all your macro requirements. im not a vegetarian, so i dont know how much help i'll be, but just spend some time on google and you'll find some good info. once you have the knowhow, get in the gym, eat, sleep, stay consistent.
heres an example of a simple routine to get you started
DAY 1
Squat - 5x5 (5 sets of 5 reps)
Bench - 5x5
Row - 5x5
Dips - 2-3 sets, anywhere up to 10 reps. dont be affraid to add weight.
DAY 2
Deadlift - 5x5
Shoulder Press - 5x5
Pullups - do 3-4 sets, work on increasing the number of reps. if you can do 10 or more, add weight
you can add accessory movements to, like bicep curl or tricep pushdown or something, but you wont need it. if you do add them, make sure you only add one to each day. throw in some ab exercises at the end of each workout. do it about 2-3 time a week. ive been doing something similar to this and its been working great.
whatever routine you choose, spend the first couple of weeks getting the form of each exercise down, dont worry about adding weight right away. youtube some of the exercises, read up on them, take videos and post them up for critiques, whatever you gotta do to make sure you have correct form, believe me when i say that that is important. good luck
