Read, read, read! Spend a lot of time reading the forums and educating yourself. If you have a question try using the search function -- most likely somebody has already asked and answered it! Understand that you will be responsible for just about everything including your own health, safety and for choosing a reliable vendor that wont rip you off. Read up on reconstituting lypholized peptides because whatever you decide to buy will be shipped to you in puck/powder form. Read up on BAC water and sterility.
Start with the peptide(s) you are most interested in, figure out what size dose and schedule you want, look into a peptide calculator to help figure out how you should reconstitute, make sure you have all the necessary supplies for reconstitution, sterility and injecting yourself, research vendors until you are more comfortable than not and then pull the trigger on buying some kits. When you receive your kit you should get a vial tested to verify that what you got in the vial is actually legitimate AND the correct amount! So make sure to budget for testing.
It took me about a month or more of basically reading this forum (and some other sources) daily before I felt "educated" enough to buy and I consider myself to be a very quick study. Theres a lot to digest but once you figure it out it becomes easier to navigate in this world of gray market but diligence and a desire to self educate is a must here.
Good luck!