Start with {{GB summits start}}. This puts the full article title in the infobox. If the article title contains a disambiguator, or you want to use a different name for any reason, then include the name as a parameter: e.g. {{GB summits start|Ben More}}.
For each summit you want to list, use the following formula: {{GB summits entry|Name=|Gridref=|Height=|Status=}}. There's no need to wikilink the entries in the "Status" field, as Listed summits at the top of the infobox links to the relevant page.
Finish with {{GB summits end}} to close the table syntax.
If the highest summit of the mountain has the same name as the mountain as a whole (e.g. Grisedale Pike), there's probably no need to include it in the summits box. If it has a different name (e.g. Stob Dearg on Buachaille Etive Mòr), it can be helpful to include it.
