You need to go to chart of accounts in settings and create/rename expense accounts so that you are only using the expense accounts that you actually need such as salaries, petrol, inventory or whatever you want to record as an expense. If you buy and sell stuff, then inventory is what you are looking for.
What I would recommend that you do is that you first create a dummy account to play with for a week or two, second you read the guides at the top of the window and lastly, get an accountant to give you an hours training session. It will save you a lot of time and hassle at years end if you get things setup properly from day one as it were. Before you start transacting, you need to have some familiarity with accounting (an accountant would be the best person to give you one hours training for your particular business needs) and you do need to play around with Manager and just familiarise yourself with how the program works.
The forum is more suited to helping people with a specific issue like how to record a dividend for a ltd company, but even that requires basic understanding of how to use spend money, create new chart of accounts and how liabilities and expenses and equity works! In short you need to have a basic understanding of accounting otherwise you will be doing things in Manager and never really understanding why you are doing xyz.
Read the guides first, then create a dummy business in manager and play with it for a few days creating transactions and seeing how it all works. Then get an accountant to adivse you on your specific setup. Then the forum would be very useful for Manager specific queries or for more advanced accounting questions.