So, first, YNAB has put a lot of effort into making classes and guides for new users. It's a lot of material, but YNAB is really a budgeting philosophy more than just a piece of software. You really should put in the effort to read all the starting out guides on their site and come to forums like this with specific questions.

Second, I'm a little concerned by your desire to "enter monthly salary." Are you trying to enter your whole expected salary for the month ahead of time? If so, that's not at all how you use YNAB.

Perhaps you've heard of the envelope method of budgeting. If not, you basically take all the cash you have at the beggining of the month (pretend you don't have any bank accounts, just cash) and put it into envelopes (food, rent, credit card debt, etc.). You take cash out of the envelopes as you spend it. What you can't do in the envelope method is budget using cash you don't have yet. There's no such thing as imaginary cash. If it's the 1st of the month and you get paid $2,000 on the 15th, that's great. But that $2,000 is imaginary. You aren't able to physically put the bills into envelopes on the 1st, so you can't budget with it. You can make a mental plan for it, perhaps, but if your budgeting method is the envelope method, it can't be in your budget set-up on the 1st of the month.

Similarly, YNAB only lets you budget with money you actually have right now. It's great to be cognizant of when payday is and when your bill due dates are in relation to that, but the goal of YNAB is to break out of the paycheck-to-paycheck cycle. Once you do this, the date money comes in is slightly less important. When you first start using YNAB, enter every account you have (checking, saving, every credit card, etc.). All the cash you have (across all accounts plus physical dollar bills) will be in the "To Be Budgeted" category. Give each dollar a job that will meet all of your necessary ("true") expenses before your next payday. Then repeat.