They can be stubborn, so take it slow.
I'm right handed, so I like to stand my birds on a table (let them stand on their own), drape my left arm over them, pull them to my body. You can sort of "wedge" them in with the elbow. Then you have your left hand free to reach and pull wattles/control the head and use the right to administer medication.
If a bird has a full crop, something like reproductive problems or a condition that may make it harder for them to breath - then them standing on their own seems less stressful for them (and easier on my back too!)
OK so you are going to syringe the medication. I still usually give mine just a few drops at a time in the beak and let them take it in.
Another option is IF you have a small syringe (I see you have mini!) then you could open the beak and put the syringe in the esophegous. See the photos and video in the link below. It's not that hard to do, I've done it either way, but most of the time I give it by drops so I can watch how they swallow and I spend more time with them LOL
https://www.backyardchickens.com/ar...er-construction-check-back-for-updates.73335/