The easy way…
No coding required
1 Create an account
First you will need to create an account with an avatar name and password here:
2 Use a third-party viewer with a grid selector
The easiest way to visit is to use one of the third-party viewers that includes a grid selector on the log-in screen.
This list is by no means exhaustive, and you may find that your current viewer has a grid selector (please mention it in the comments!). Check its Preferences — the setting to show the grid selector on the log-in screen may be in the “Advanced” settings.
3 Log in
At the log-in screen, simply choose “OSgrid” from the grid selector’s drop-down menu, then log in with the avatar name and password you registered with at step 1.
4 Sort out avatar
You are likely to land at Lbsa Plaza or Wright Plaza.
Lbsa Plaza usually has people who are happy to help new visitors to the grid.
Wright Plaza has lots of freebie stores within walking/flying distance.
Use the viewer’s World Map to search for Anarta and Colorado’s K’Veer, or for Devokan Tao which has working linking books to various Myst/Uru-style regions on OSgrid (including K’Veer).