My very first hang was in a Hammocka and under a Walmart blue tarp just like yours! Those pictures bring back memories! I spent my night trying not to slide down towards the foot of the hammock. I was hanging with nylon tubular webbing from REI, and it stretched overnight. I didn't have a clue it was best to have the feet higher than the head end at that time, either. I soon discovered I needed a longer hammock. I think mine was shorter than it was supposed to be according to the specs I read later. Either way, I still loved it!
Have fun learning. I sure have. I don't have much as far as technical advice, but I wanted you to know you aren't the only one who started out with that setup!