In this order: warm the crib with a wheat pack (a next to bed one with a fold down side as others have suggested), change nappy, check they're dressed to the room temperature (lots of handy infographics on the web about how much they should be wearing), swaddle (love to dream if they like their arms up, any other zippy one or velcro one of not - make life easy for yourself!), big feed (keep waking them to ensure they have a full feed if they're a sleepy snacker), wind really well during and after feed (look for tips on the internet- it's really important to stop them being uncomfortable lying down), soothe (have them turned into you so their tummy is against yours and pat their back/bottom firmly and rhythmically), remove heat pack, put down in crib, repeat soothing if needed until they go down to sleep or are at least quiet in the crib (Experiment with how sleepy you need to get them before putting them down).
A bedtime routine including something you don't do at other times of day, like a bath, can help signal nighttime to them as time goes on too.
Go to sleep as soon as they do, don't sit around wondering if they're about to wake up again, like I did! They might, but you'll soon know about it and you'll have gained nothing from your vigil.
If you're nervous about leaving them to sleep without watching over them, invest in a good breathing/heart rate monitor. It's not really for them, as they are likely to be absolutely fine, it's for your peace of mind to allow you to sleep.
Agree with your partner some form of sharing the load for a few nights at least to get some sanity back. You might alternate responsibility for feeding and soothing on an alternate nights basis or, say, them on duty for the first half of the night, you for the second. If you're breastfeeding, partner just brings them to you for a good full feed before taking them away to settle back. Sleep somewhere else when you're 'off duty' to get a proper stretch of sleep. Spare room, currently unused nursery, sofa... Wherever your not going to be woken immediately by baby being up.
Step 2 - kill the unhelpful midwife who suggested you ought to martyr yourself to your child to the point of getting no sleep. This makes me so angry. Sleep deprivation is a recognised form of torture and it seriously messes with the human body and mental health. Honestly, no wonder postnatal depression is rife!
Good luck!