You are on the right track, but right now you are biting off more than you can chew. You need to get a good grasp of the basic shape before you can play that chord.
Let's look a the shape:
E -10
B -8
G -8
D -6
A -8
E --
The way to play this is to use your 1st finger on the D string, use your 2nd finger on the A string, use your 3rd finger for the B and G string, and use your 4th finger on the E string. It's not the easily shape right now so let's simplify it just for a moment. Right now we will forget about the 10 on the high E string and just bar the E, B , and G string with your 3rd finger to give us this shape:
E -8
B -8
G -8
D -6
A -8
E --
Is it still too hard to bar the 3 strings? Lets take the shape up to the 12 fret:
E -12
B -12
G -12
D -10
A -12
E ---
Is it still too hard to bar the 3 strings? Then we need to make your 3rd finger stronger. Just barring those 3 string with your 3rd finger and making sure all ring out should be a good finger strength exercise:
E -12--11--10--9--8--7--6--5--4--3--2--1
B -12--11--10--9--8--7--6--5--4--3--2--1
G -12--11--10--9--8--7--6--5--4--3--2--1
D --------------------------------------
A --------------------------------------
E --------------------------------------
If your fingers aren't strong enough for a certain shape, you need to make the stronger through practice. It's not always easy, but it's what you have to do.