If you already know the region of an assembly that you are interested in, type a query of the form scaffold_name:start-end
into the search box in the ensembl.
subdomain to jump directly to that location in the genome browser.
This example uses positions 2100 to 2200 of Heliconius melpomene melpomene Hmel2 scaffold Hmel200129 on LepBase.
1. Visit ensembl.lepbase.org and click on the Heliconius melpomene melpomene Hmel2 assembly:

2. Type the scaffold_name:start-end coordinates “Hmel200129:2100-2200” into the search box at the top right of the screen and press enter:

3. The search should redirect you to the location view for scaffold Hmel200129, focussed on coordinates 2100-2200. The Region in detail view shows that this scaffold has a single gene, HMEL021227g1 (red bar) on the forward strand (> arrow after the gene name) and that these coordinates span the end of the gene :

4. Scroll to the bottom of the page for a more detailed view showing the sequence of this region as coloured bars. This assembly has variation data available so there is also a track showing sequence variants as coloured blocks, two green blocks indicate synonymous variants while the two yellow boxes show the locations of missense variants.

5. Click on one of the variant blocks to bring up a menu with links to more information about the variant:
