Hi,
If you have uploaded your DNA to GEDmatch you should now have a "code" or ID number (for example mine is M105207) which is what people will ask you for if they want to compare your DNA with theirs.
However, once you have that code it means your profile is in the database and will appear in search results of one to many for example - you can search for all the people who match you in descending segment size order. The advantage of this site is that it is free and combines profiles of people who have tested on all the other sites.
You mention people avoiding payment - it's a free site! There are some extras you can pay for but there is no need to unless you particularly want to and certainly not until you are completely happy with all the free aspects of it. I occasionally pay for a month of Tier 1 but only if I know I'm going to have time to do lots of work on my DNA matches. Free access gives you all the details of your matches.
I would recommend having a look at some of the tutorials on YouTube - there are lots like this one
https://www.youtube.com/watch?v=id7JJ1NoTNk and they get progressively more detailed. These videos can also be accessed via the site.
It is a fantastic site and can really help with DNA but needs a bit of getting used to.
Liz