To log a ride, add a post containing all of your 2017 metric centuries to date. One ride per line, with the date, distance, short route description, and any links you want to add. Do not post just a link.
When you add a post, copy all of the rides from your previous post so that your latest post contains all of your rides.
It is great to see so many riders accepting this challenge and the number who are riding more than just one per month. I am genuinely interested in where people are riding and look for interesting route choices and implicit recommendations for 'good' roads. However.
At the risk of not just being recognised but also 'called out' (is that the modern vernacular) as a grumpy old man, I'm going to make a point that I have been restraining myself from making for a few months, so here goes.
The imperial century people (of whom I am one this year - not double counting) invite participants to record (only) their 'first' century of the month by editing their original (ie January) post. In the metric century crew we invite participants to record each 100km+ ride as a new post, pasting their previous post in. This creates more posts, which is fine.
But this thread later in the year ie from April onwards, risks becoming less attractive if "the Rules" are not followed. Specifically the 'rule' being wantonly and (imo) lazily broken is the specification "one ride per line". If people don't adhere to this, the posts become long and unwieldy, which impacts on the thread and its readers (ie you (all) and me). The 'more than 2 line' merchants know who they are and substantial 'adaption' would be required. (note I am not naming them - if the hat fits; etc). But with very little effort the following posters could get each of their rides down to one line (and see the ways of doing this listed below):
@Donger @Osprey @13 rider - and join the good practice brigade (qv).
On the plus side have a look at my,
@Sea of vapours,
@Sbudge,
@StuartG or
@Goonerobes posts for examples of good practice.
I offer the following suggestions to those who have difficulty:
1) Avoid blank lines.
2) Embed links (eg Stava, RwGPS) in the distance as opposed to as a 'stand-alone' paste. You do this as follows: block the distance (eg 107km) and click the 'link' icon (seventh along in tool bar immediately above), swap windows to your route recording and copy the link, revert to CC - the pop-up window you've left there - and then paste in the hyperlink.
3) This is the Metric Century challenge - no "miles". 3 characters more than 'km'; 4 if you count the space.
4) Itinerary ie list of places passed through. Precis this list to the essential places. If I (and others) can do so, so can you. From (in my case) RwGPS, I paste the list into the draft post and then cut till I can get it all on one line (accept I did not manage this for the 600). If people want to look (in detail) where you went they'll click the link.
In the spirit of many more 'hundreds', please don't let this suggestion deter any 'challenger' from posting the rides of which they can be justly proud, using as many lines as they think others will appreciate.
I got the .3 right but a mile short 
so after a quick coffee it's back on the bike to the next village and back and 3 more miles . Please forgive my miscalulation
