A cycling vo2 max. is required to get suggestion

7138175 said:

I should have power meter

yes. This is required.

7138175 said:

and HRM

This is optional, but better as wrist HR are not great with biking and you want good HR data for your VO2 Max estimate.

7138175 said:

and then what I should to do?

1- make sure your HR Max is correct. Don't rely on a formula. If your doctor lets you, run your 5k PB with a chest strap. Take the peak HR and add 5bpm. At least, if you use the watch HR max detection, you will know if the detection is about correct.

2- go bike for at least 10mn at 70% of your HR Max. This will give you a first estimate.

3- Improve your estimates over time. Follow the daily suggestions, trying to keep your work load in the "green zone". But keep the training focus balanced to expose the watch to a variety of efforts.

I have the same issue, but I don't understand the text above on what to do to be able to see suggestions for my training.

What exactly should I do to get the suggestions?

7187733 said:

What exactly should I do to get the suggestions?

Suggestions are only for biking (road, MTB, etc.) and running (road. trail, track, etc.). They don't show for other activities.

To see them, press the start button, choose run or bike, go to settings > training > workouts > daily suggestions

I am choosing for biking but I get the message "A cycling vo2 max. is required to get suggestion" 

When you go to the performance glance, do you see both a running V02 max and a cycling VO2 Max?

Alternatively, when you go to your training status in Garmin Connect, under VO2 Max, do you see a chart with 2 VO2 Max “pie charts”?

Yes, and Etupes25 has described the necessary steps to get a cycling VO2Max. Just READ his first post.

TL;DR: You need a bike with powermeter and have to train with it outdoors. If you don't have that, there is no other possibility of getting a cycling VO2Max.