STEP 1: Identify how much alcohol you will be drinking
Myfitnesspal is not the best tool to track alcohol, as it typically it doesn't have the correct calories and macros assigned to the alcohol. Drink aware is a great tool to give you an estimate pf calories in popular drinks.
Step 2: Convert alcohol into carbs and fats, NEVER protein
When tracking alcohol, you should be taking away from your carb or fat allowance. To do this you need to be aware carbs contain 4 calories per 1g and fats contain 9 calories per 1g.
Using carbs: 175ml Glass of red wine = 159 calories - You then do 159 divided by 4, which = 39.75g of carbs
Using fats: 175ml Glass of red wine = 159 calories - You then do 159 divided by 9, which = 17.6g of fats.
Using 50/50: 175ml Glass of red wine = 159 calories - You then do 79.5 divided by 4, which = 19.8g carbs and 79.5 divided by 9, which = 8.8g fats
Which ever way you prefer, that is your choice but NEVER use protein!
Step 3: How to put the above into Myfitnesspal
1. Add food
2. Search food
3. Type in carbs or fats, depending which one you want to use
4. Type correct amount
Plan ahead if possible
If you do the above at the begging of your day, you can workout out the rest of your calories around it, focusing on getting you protein and fibre as a priority and leaving either carbs or fats to make up the rest of your alcohol calories.
If for whatever reason you end up drinking more than you logged, DON'T PANIC, just account for it and make up for it the following day.
Life is to be enjoyed and alcohol is a huge part of this, however make sure this is not a daily occurrence and if long term is your health minimal alcohol should be consumed.